Change Unit.multiplier type from decimal to float

Remove remnants related to BigDecimal.

.gitignore

@@ -15,6 +15,9 @@
 /config/master.key
 /config/puma.rb
 
+# Ignore test database.
+/db/test.sqlite3
+
 # Ignore all logfiles and tempfiles.
 /log/*
 /tmp/*
@@ -30,7 +33,7 @@
 
 /tmp/restart.txt
 
-# Ignore user files
+# Ignore user files.
 /.bash_history
 /.byebug_history
 /.config
@@ -38,6 +41,7 @@
 /.lesshst
 /.local
 /.mysql_history
+/.sqlite_history
 /.ssh
 /.vim
 /.viminfo

CLAUDE.md

@@ -1,84 +0,0 @@
-# CLAUDE.md
-
-This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
-
-## Project Overview
-
-Fixin.me is a "quantified self" Rails 7.2.3 application for personal data tracking. Users define hierarchical **quantities** (metrics to track), **units** (with optional conversion hierarchies), and **readouts** (individual measurements). There is also a non-persistent **measurement** model used as a form wrapper.
-
-## Setup
-
-Configuration files are distributed as `.dist` templates — copy and customize before use:
-
-```bash
-cp config/application.rb.dist config/application.rb
-cp config/database.yml.dist config/database.yml
-cp config/puma.rb.dist config/puma.rb
-```
-
-```bash
-bundle config --local frozen true
-bundle config --local path .gem
-bundle config --local with mysql development test   # or: pg, sqlite
-bundle install
-RAILS_ENV=development bundle exec rails db:create db:migrate db:seed
-```
-
-## Common Commands
-
-```bash
-bundle exec rails s                                          # start server
-bundle exec rails test                                       # all unit/model/controller tests
-bundle exec rails test:system                                # all system tests (Capybara + Selenium)
-bundle exec rails test test/system/units_test.rb            # single test file
-bundle exec rails test --seed 64690 --name test_add_unit    # single test by name
-bundle exec rails db:seed:export                             # export default settings as seed file
-```
-
-## Architecture
-
-### Data Model
-
-- **Quantity** — hierarchical tree (self-referential `parent_id`). Cached `depth` and `pathname` fields are recomputed via recursive CTEs on write. Direct assignment to cached fields is blocked.
-- **Unit** — optional hierarchy via `base_id` and `multiplier` for unit conversion. Multiplier precision/scale is validated by a custom validator.
-- **Readout** — single measurement: `value` (IEEE 754 float), `quantity`, `unit`, `category`.
-- **Measurement** — `ActiveModel::Model` form wrapper (not database-backed); bridges the readout creation form.
-- **User** — Devise-managed with a status enum: `admin`, `active`, `restricted`, `locked`, `disabled`. Admins can disguise as other users.
-
-### Hierarchical Queries
-
-Both `Quantity` and `Unit` use recursive CTEs for tree traversal (ordered traversal, ancestors, progenies, common ancestors). `lib/core_ext/arel/` patches Arel to support CTE with `UPDATE`/`DELETE` statements, working around Rails issue #54658.
-
-### Custom Extensions (`lib/core_ext/`)
-
-- **arel/** — CTE support for UPDATE/DELETE
-- **active_model/** — precision/scale validator used by `Unit#multiplier`
-- **active_record/** — `attr_cached` mechanism (see `ApplicationRecord`)
-- **action_view/** — record identifier suffixes
-- Miscellaneous: `Array#delete_bang`, `BigDecimal` scientific notation
-
-### Response Handling
-
-Controllers respond to both HTML and Turbo Stream formats. Errors during Turbo Stream requests trigger a redirect with flash rather than rendering inline, handled in `ApplicationController`.
-
-### Numeric Precision
-
-Readout values are stored as IEEE 754 double-precision floats (not fixed-point decimals). Rationale in `DESIGN.md`: biological values span many orders of magnitude; 15-digit float precision is sufficient and avoids conversion overhead.
-
-### Routes
-
-```
-measurements   GET/POST /measurements
-readouts       GET/POST /readouts, DELETE /readouts/:id/discard
-quantities     CRUD + POST /quantities/:id/reparent
-units          CRUD + POST /units/:id/rebase
-users          CRUD + POST /users/:id/disguise, POST /users/revert
-default/       namespace for default units import/export and admin panel
-root           → /units (authenticated), /sign_in (unauthenticated)
-```
-
-## Database Requirements
-
-The database must support:
-- Recursive CTEs with `UPDATE`/`DELETE` (MySQL ≥ 8.0, PostgreSQL, or SQLite3)
-- Decimal precision of 30+ digits

DESIGN.md

@@ -22,13 +22,38 @@ whenever a change is considered, to avoid regressions.
           and scale approximately half of that - 9,
     * double precision floating point guarantees 15 digits of precision, which
       is more than enough for all expected use cases,
+        * if a decimal string with at most 15 significant digits is converted to
+          the IEEE 754 double-precision format, giving a normal number, and then
+          converted back to a decimal string with the same number of digits, the
+          final result should match the original string,
+        * if an IEEE 754 double-precision number is converted to a decimal
+          string with at least 17 significant digits, and then converted back to
+          double-precision representation, the final result must match the
+          original number,
         * single precision floating point only guarntees 6 digits of precision,
           which is estimated to be too low for some use cases (e.g. storing
-          latitude/longitude with a resolution grater than 100m)
+          latitude/longitude with a resolution grater than 100m),
 * double precision floating point (IEEE 754) is a standard that ensures
-  compatibility with all database engines,
+  compatibility with majority of database engines,
     * the same data format is used internally by Ruby as a `Float`; it
       guarantees no conversions between storage and computation,
     * as a standard with hardware implementations ensures both: computing
       efficiency and hardware/3rd party library compatibility as opposed to Ruby
-      custom `BigDecimal` type
+      custom `BigDecimal` type,
+    * at present, only normalized numbers are used and considered sufficient, in
+      order to avoid potential issues with the cross-platform compatibility of
+      subnormal (denormal) numbers,
+* in the future, the IEEE 754 decimal64 data type may be considered once it is
+  supported by database engines.
+
+### Database layer vs application layer data model constraints
+
+* database constraints are the final guard against data integrity corruption,
+    * they should safeguard against data referential integrity loss under _all_
+      data (not schema) manipulation scenarios, including application level
+      logic errors and direct data manipulation (e.g. through `dbconsole`),
+* application constraints can be as restrictive as database constraints or more,
+  but not less, as it doesn't serve any use case,
+    * proper application level constraints should prevent unhandled database
+      exception occurences, e.g `ActiveRecord::InvalidForeignKey` for operations
+      performed through Models (i.e. not `#delete_all` etc.)

Gemfile

@@ -1,14 +1,18 @@
 source "https://rubygems.org"
 
 # The requirement for the Ruby version comes from Rails
-gem "rails", "~> 7.2.3"
+# NOTE: after updating Rails make sure that schema dump is not sorted:
+#   v8.1.3/activerecord/lib/active_record/schema_dumper.rb#L195
+# Waiting for this change to be reverted/configuration setting added:
+# https://github.com/rails/rails/pull/56842, https://github.com/rails/rails/pull/55414
+gem "rails", "~> 8.1.3"
 gem "sprockets-rails"
 gem "puma", "~> 6.0"
 gem "sassc-rails"
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem "tzinfo-data", platforms: %i[ mingw mswin x64_mingw jruby ]
 
-# TODO: select db gems automatically
+# TODO: select db gems automatically?
 #   database_config = ERB.new(File.read("config/database.yml")).result
 #   YAML.load(database_config, aliases: true).values.map { |env| env["adapter"] }.uniq
 group :mysql, optional: true do
@@ -42,11 +46,4 @@ group :test do
   # Use system testing [https://guides.rubyonrails.org/testing.html#system-testing]
   gem "capybara"
   gem "selenium-webdriver"
-
-  # Remove minitest version restriction after error fixed:
-  #   railties-7.2.3/lib/rails/test_unit/line_filtering.rb:7:in `run':
-  #     wrong number of arguments (given 3, expected 1..2) (ArgumentError)
-  #   from /var/www/.gem/ruby/3.3.0/gems/minitest-6.0.2/lib/minitest.rb:473:in
-  #     `block (2 levels) in run_suite'
-  gem "minitest", "< 6"
 end

Gemfile.lock

@@ -1,85 +1,85 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (7.2.3)
-      actionpack (= 7.2.3)
-      activesupport (= 7.2.3)
+    action_text-trix (2.1.18)
+      railties
+    actioncable (8.1.3)
+      actionpack (= 8.1.3)
+      activesupport (= 8.1.3)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
       zeitwerk (~> 2.6)
-    actionmailbox (7.2.3)
-      actionpack (= 7.2.3)
-      activejob (= 7.2.3)
-      activerecord (= 7.2.3)
-      activestorage (= 7.2.3)
-      activesupport (= 7.2.3)
+    actionmailbox (8.1.3)
+      actionpack (= 8.1.3)
+      activejob (= 8.1.3)
+      activerecord (= 8.1.3)
+      activestorage (= 8.1.3)
+      activesupport (= 8.1.3)
       mail (>= 2.8.0)
-    actionmailer (7.2.3)
-      actionpack (= 7.2.3)
-      actionview (= 7.2.3)
-      activejob (= 7.2.3)
-      activesupport (= 7.2.3)
+    actionmailer (8.1.3)
+      actionpack (= 8.1.3)
+      actionview (= 8.1.3)
+      activejob (= 8.1.3)
+      activesupport (= 8.1.3)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (7.2.3)
-      actionview (= 7.2.3)
-      activesupport (= 7.2.3)
-      cgi
+    actionpack (8.1.3)
+      actionview (= 8.1.3)
+      activesupport (= 8.1.3)
       nokogiri (>= 1.8.5)
-      racc
-      rack (>= 2.2.4, < 3.3)
+      rack (>= 2.2.4)
       rack-session (>= 1.0.1)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actiontext (7.2.3)
-      actionpack (= 7.2.3)
-      activerecord (= 7.2.3)
-      activestorage (= 7.2.3)
-      activesupport (= 7.2.3)
+    actiontext (8.1.3)
+      action_text-trix (~> 2.1.15)
+      actionpack (= 8.1.3)
+      activerecord (= 8.1.3)
+      activestorage (= 8.1.3)
+      activesupport (= 8.1.3)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (7.2.3)
-      activesupport (= 7.2.3)
+    actionview (8.1.3)
+      activesupport (= 8.1.3)
       builder (~> 3.1)
-      cgi
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (7.2.3)
-      activesupport (= 7.2.3)
+    activejob (8.1.3)
+      activesupport (= 8.1.3)
       globalid (>= 0.3.6)
-    activemodel (7.2.3)
-      activesupport (= 7.2.3)
-    activerecord (7.2.3)
-      activemodel (= 7.2.3)
-      activesupport (= 7.2.3)
+    activemodel (8.1.3)
+      activesupport (= 8.1.3)
+    activerecord (8.1.3)
+      activemodel (= 8.1.3)
+      activesupport (= 8.1.3)
       timeout (>= 0.4.0)
-    activestorage (7.2.3)
-      actionpack (= 7.2.3)
-      activejob (= 7.2.3)
-      activerecord (= 7.2.3)
-      activesupport (= 7.2.3)
+    activestorage (8.1.3)
+      actionpack (= 8.1.3)
+      activejob (= 8.1.3)
+      activerecord (= 8.1.3)
+      activesupport (= 8.1.3)
       marcel (~> 1.0)
-    activesupport (7.2.3)
+    activesupport (8.1.3)
       base64
-      benchmark (>= 0.3)
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.3.1)
       connection_pool (>= 2.2.5)
       drb
       i18n (>= 1.6, < 2)
+      json
       logger (>= 1.4.2)
       minitest (>= 5.1)
       securerandom (>= 0.3)
       tzinfo (~> 2.0, >= 2.0.5)
-    addressable (2.8.8)
+      uri (>= 0.13.1)
+    addressable (2.9.0)
       public_suffix (>= 2.0.2, < 8.0)
     base64 (0.3.0)
-    bcrypt (3.1.21)
-    benchmark (0.5.0)
-    bigdecimal (4.0.1)
+    bcrypt (3.1.22)
+    bigdecimal (4.1.2)
     bindex (0.8.1)
     builder (3.3.0)
     byebug (13.0.0)
@@ -93,28 +93,27 @@ GEM
       rack-test (>= 0.6.3)
       regexp_parser (>= 1.5, < 3.0)
       xpath (~> 3.2)
-    cgi (0.5.1)
     concurrent-ruby (1.3.6)
     connection_pool (3.0.2)
     crass (1.0.6)
     date (3.5.1)
-    devise (5.0.2)
+    devise (5.0.3)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
       railties (>= 7.0)
       responders
       warden (~> 1.2.3)
     drb (2.2.3)
-    erb (6.0.2)
+    erb (6.0.4)
     erubi (1.13.1)
-    ffi (1.17.3-aarch64-linux-gnu)
-    ffi (1.17.3-aarch64-linux-musl)
-    ffi (1.17.3-arm-linux-gnu)
-    ffi (1.17.3-arm-linux-musl)
-    ffi (1.17.3-arm64-darwin)
-    ffi (1.17.3-x86_64-darwin)
-    ffi (1.17.3-x86_64-linux-gnu)
-    ffi (1.17.3-x86_64-linux-musl)
+    ffi (1.17.4-aarch64-linux-gnu)
+    ffi (1.17.4-aarch64-linux-musl)
+    ffi (1.17.4-arm-linux-gnu)
+    ffi (1.17.4-arm-linux-musl)
+    ffi (1.17.4-arm64-darwin)
+    ffi (1.17.4-x86_64-darwin)
+    ffi (1.17.4-x86_64-linux-gnu)
+    ffi (1.17.4-x86_64-linux-musl)
     globalid (1.3.0)
       activesupport (>= 6.1)
     i18n (1.14.8)
@@ -124,13 +123,14 @@ GEM
       activesupport (>= 6.0.0)
       railties (>= 6.0.0)
     io-console (0.8.2)
-    irb (1.17.0)
+    irb (1.18.0)
       pp (>= 0.6.0)
       prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
+    json (2.19.4)
     logger (1.7.0)
-    loofah (2.25.0)
+    loofah (2.25.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
     mail (2.9.0)
@@ -142,10 +142,12 @@ GEM
     marcel (1.1.0)
     matrix (0.4.3)
     mini_mime (1.1.5)
-    minitest (5.27.0)
+    minitest (6.0.6)
+      drb (~> 2.0)
+      prism (~> 1.5)
     mysql2 (0.5.7)
       bigdecimal
-    net-imap (0.6.3)
+    net-imap (0.6.4)
       date
       net-protocol
     net-pop (0.1.2)
@@ -155,21 +157,21 @@ GEM
     net-smtp (0.5.1)
       net-protocol
     nio4r (2.7.5)
-    nokogiri (1.19.1-aarch64-linux-gnu)
+    nokogiri (1.19.3-aarch64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.19.1-aarch64-linux-musl)
+    nokogiri (1.19.3-aarch64-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.19.1-arm-linux-gnu)
+    nokogiri (1.19.3-arm-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.19.1-arm-linux-musl)
+    nokogiri (1.19.3-arm-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.19.1-arm64-darwin)
+    nokogiri (1.19.3-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.19.1-x86_64-darwin)
+    nokogiri (1.19.3-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.19.1-x86_64-linux-gnu)
+    nokogiri (1.19.3-x86_64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.19.1-x86_64-linux-musl)
+    nokogiri (1.19.3-x86_64-linux-musl)
       racc (~> 1.4)
     orm_adapter (0.5.0)
     pg (1.6.3)
@@ -186,32 +188,32 @@ GEM
     psych (5.3.1)
       date
       stringio
-    public_suffix (7.0.2)
+    public_suffix (7.0.5)
     puma (6.6.1)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (3.2.5)
-    rack-session (2.1.1)
+    rack (3.2.6)
+    rack-session (2.1.2)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
     rack-test (2.2.0)
       rack (>= 1.3)
     rackup (2.3.1)
       rack (>= 3)
-    rails (7.2.3)
-      actioncable (= 7.2.3)
-      actionmailbox (= 7.2.3)
-      actionmailer (= 7.2.3)
-      actionpack (= 7.2.3)
-      actiontext (= 7.2.3)
-      actionview (= 7.2.3)
-      activejob (= 7.2.3)
-      activemodel (= 7.2.3)
-      activerecord (= 7.2.3)
-      activestorage (= 7.2.3)
-      activesupport (= 7.2.3)
+    rails (8.1.3)
+      actioncable (= 8.1.3)
+      actionmailbox (= 8.1.3)
+      actionmailer (= 8.1.3)
+      actionpack (= 8.1.3)
+      actiontext (= 8.1.3)
+      actionview (= 8.1.3)
+      activejob (= 8.1.3)
+      activemodel (= 8.1.3)
+      activerecord (= 8.1.3)
+      activestorage (= 8.1.3)
+      activesupport (= 8.1.3)
       bundler (>= 1.15.0)
-      railties (= 7.2.3)
+      railties (= 8.1.3)
     rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
@@ -219,29 +221,28 @@ GEM
     rails-html-sanitizer (1.7.0)
       loofah (~> 2.25)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
-    railties (7.2.3)
-      actionpack (= 7.2.3)
-      activesupport (= 7.2.3)
-      cgi
+    railties (8.1.3)
+      actionpack (= 8.1.3)
+      activesupport (= 8.1.3)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
       tsort (>= 0.2)
       zeitwerk (~> 2.6)
-    rake (13.3.1)
+    rake (13.4.2)
     rdoc (7.2.0)
       erb
       psych (>= 4.0.0)
       tsort
-    regexp_parser (2.11.3)
+    regexp_parser (2.12.0)
     reline (0.6.3)
       io-console (~> 0.5)
     responders (3.2.0)
       actionpack (>= 7.0)
       railties (>= 7.0)
     rexml (3.4.4)
-    rubyzip (3.2.2)
+    rubyzip (3.3.0)
     sassc (2.4.0)
       ffi (~> 1.9)
     sassc-rails (2.1.2)
@@ -251,7 +252,7 @@ GEM
       sprockets-rails
       tilt
     securerandom (0.4.1)
-    selenium-webdriver (4.41.0)
+    selenium-webdriver (4.43.0)
       base64 (~> 0.2)
       logger (~> 1.4)
       rexml (~> 3.2, >= 3.2.5)
@@ -265,32 +266,32 @@ GEM
       actionpack (>= 6.1)
       activesupport (>= 6.1)
       sprockets (>= 3.0.0)
-    sqlite3 (2.9.0-aarch64-linux-gnu)
-    sqlite3 (2.9.0-aarch64-linux-musl)
-    sqlite3 (2.9.0-arm-linux-gnu)
-    sqlite3 (2.9.0-arm-linux-musl)
-    sqlite3 (2.9.0-arm64-darwin)
-    sqlite3 (2.9.0-x86_64-darwin)
-    sqlite3 (2.9.0-x86_64-linux-gnu)
-    sqlite3 (2.9.0-x86_64-linux-musl)
+    sqlite3 (2.9.3-aarch64-linux-gnu)
+    sqlite3 (2.9.3-aarch64-linux-musl)
+    sqlite3 (2.9.3-arm-linux-gnu)
+    sqlite3 (2.9.3-arm-linux-musl)
+    sqlite3 (2.9.3-arm64-darwin)
+    sqlite3 (2.9.3-x86_64-darwin)
+    sqlite3 (2.9.3-x86_64-linux-gnu)
+    sqlite3 (2.9.3-x86_64-linux-musl)
     stringio (3.2.0)
     thor (1.5.0)
     tilt (2.7.0)
-    timeout (0.6.0)
+    timeout (0.6.1)
     tsort (0.2.0)
     turbo-rails (2.0.23)
       actionpack (>= 7.1.0)
       railties (>= 7.1.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
+    uri (1.1.1)
     useragent (0.16.11)
     warden (1.2.9)
       rack (>= 2.0.9)
-    web-console (4.2.1)
-      actionview (>= 6.0.0)
-      activemodel (>= 6.0.0)
+    web-console (4.3.0)
+      actionview (>= 8.0.0)
       bindex (>= 0.4.0)
-      railties (>= 6.0.0)
+      railties (>= 8.0.0)
     websocket (1.2.11)
     websocket-driver (0.8.0)
       base64
@@ -315,11 +316,10 @@ DEPENDENCIES
   capybara
   devise
   importmap-rails
-  minitest (< 6)
   mysql2 (~> 0.5)
   pg (~> 1.5)
   puma (~> 6.0)
-  rails (~> 7.2.3)
+  rails (~> 8.1.3)
   sassc-rails
   selenium-webdriver
   sprockets-rails

README.md

@@ -16,14 +16,10 @@ environment, see the _Contributing_ section below.
 * Server side:
     * Ruby interpreter, depending on the version of Rails used (see _Gemfile_),
         * https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#ruby-versions
-    * database (e.g. MySQL >= 8.0) supporting:
+    * database (e.g. SQLite, MySQL >= 8.0) supporting:
         * recursive Common Table Expressions (CTE) for SELECT/UPDATE/DELETE,
             * MariaDB does not support CTE for UPDATE/DELETE
               (https://jira.mariadb.org/browse/MDEV-18511)
-        * decimal datatype with precision of at least 30,
-            * SQLite3 _flexible typing_ decimal will work, but precision
-              will be limited to 16, making it practical mostly for testing
-              purposes
     * for testing: browser as specified in _Client side_ requirements
 * Client side:
     * browser (e.g. Firefox >= 121) supporting:
@@ -89,14 +85,10 @@ Running
 
 ### Standalone Rails server + Apache proxy
 
-Customize Puma config template:
+Copy and customize Puma config template if required:
 
     cp -a config/puma.rb.dist config/puma.rb
 
-and specify server IP/port, either with `port` or `bind`, e.g.:
-
-    bind 'tcp://0.0.0.0:3000'
-
 #### (option 1) Start server manually
 
     bundle exec rails s -e production
@@ -123,9 +115,10 @@ Contributing
 
 ### Gems
 
-Apart from database adapter, install development and testing gems:
+Install development and testing gems, including at least MySQL and SQLite
+database adapters:
 
-    bundle config --local with mysql development test
+    bundle config --local with development test mysql sqlite
 
 ### Configuration
 
@@ -138,20 +131,29 @@ assets.
 
 ### Database
 
-Grant database user privileges for development and test environments,
-possibly with different Ruby versions:
+Grant database user privileges for development and test environments. Example
+below shows how to grant privileges to all databases which names start with
+`fixinme-` on MySQL:
 
     > mysql -p
     mysql> create user `fixinme-dev`@localhost identified by '<some password>';
     mysql> grant all privileges on `fixinme-%`.* to `fixinme-dev`@localhost;
     mysql> flush privileges;
 
+Dumping development data before database reset:
+
+    mysqldump -h <address> -u <user> -p --no-create-info --no-tablespaces --complete-insert <database> > tmp/data.sql
+
 ### Development environment
 
 Starting application server in development environment:
 
     bundle exec rails s -e development
 
+Accessing database console when more than one test db is present:
+
+    bundle exec rails dbconsole -e test --db sqlite3
+
 For running rake tasks, prepend command with environment:
 
     RAILS_ENV=development bundle exec rails ...
@@ -164,14 +166,22 @@ Tests need to be run from within toplevel application directory:
 
         bundle exec rails test:system
 
-* system test(s) with seed/test name specified:
+* system test(s) with seed or test name specified:
 
-        bundle exec rails test:system --seed 64690 --name test_add_unit
+        bundle exec rails test:system --include test_add_unit --seed 64690
 
-* all tests from one file, with optional seed:
+* all tests from one file, optionally with seed:
 
         bundle exec rails test test/system/users_test.rb --seed 1234
 
+* system tests for selected database configuration (if multiple present):
+
+        bundle exec rails test:system --include /^test_sqlite3_/
+
+* single system test for all database configurations (if multiple present):
+
+        bundle exec rails test:system --include /^test_\\w+_add_unit$/
+
 ### Icons
 
 Pictogrammers Material Design Icons: https://pictogrammers.com/library/mdi/

app/assets/stylesheets/application.css

@@ -231,12 +231,17 @@ textarea:invalid {
   text-decoration: underline 1px var(--color-border-gray);
   text-underline-offset: 0.25em;
 }
-[name=cancel],
 .auxiliary {
-  border-color: var(--color-border-gray);
+  border-color: var(--color-nav-gray);
   color: var(--color-nav-gray);
   fill: var(--color-nav-gray);
 }
+table .button {
+  border-color: var(--color-border-gray);
+  font-weight: normal;
+  height: 100%;
+  padding: 0.4em;
+}
 .button:focus-visible,
 .tab:focus-visible,
 .tab:hover {
@@ -259,13 +264,6 @@ textarea:invalid {
   color: var(--color-blue);
   text-decoration-color: var(--color-blue);
 }
-table .button {
-  border-color: var(--color-border-gray);
-  color: var(--color-table-gray);
-  font-weight: normal;
-  height: 100%;
-  padding: 0.4em;
-}
 
 
 /* NOTE: collapse gaps around empty rows (`topside`) once possible with
@@ -360,20 +358,20 @@ header {
   line-height: 2.2em;
   pointer-events: auto;
 }
-.flash:before {
-  filter: invert();
+.flash::before {
+  filter: invert(1);
   height: 1.4em;
   margin: 0 0.5em;
   width: 1.4em;
 }
-.flash.alert:before {
+.flash.alert::before {
   content: url('pictograms/alert-outline.svg');
 }
 .flash.alert {
   border-color: var(--color-red);
   background-color: var(--color-red);
 }
-.flash.notice:before {
+.flash.notice::before {
   content: url('pictograms/check-circle-outline.svg');
 }
 .flash.notice {
@@ -437,15 +435,18 @@ header {
 
 .tabular-form table {
   border: none;
-  border-spacing: 0.4em 0;
-  margin-inline: -0.4em;
+  border-spacing: 0;
 }
 .tabular-form table td {
   border: none;
+  padding-inline-start: 0.4em;
   vertical-align: middle;
 }
-.tabular-form table td {
-  padding-inline: 0;
+.tabular-form table td:first-child {
+  padding-inline-start: 0;
+}
+.tabular-form table td:last-child {
+  padding-inline-end: 0;
 }
 .tabular-form table :is(form, input, select, textarea):only-child {
   margin-inline-start: 0;

app/controllers/quantities_controller.rb

@@ -8,10 +8,6 @@ class QuantitiesController < ApplicationController
     raise AccessForbidden unless current_user.at_least(:active)
   end
 
-  before_action only: [:new, :edit, :create, :update] do
-    @user_units = current_user.units.ordered
-  end
-
   def index
     @quantities = current_user.quantities.ordered.includes(:parent, :subquantities)
   end

app/controllers/readouts_controller.rb

@@ -6,7 +6,7 @@ class ReadoutsController < ApplicationController
   def new
     @quantities -= @prev_quantities
     # TODO: raise ParameterInvalid if new_quantities.empty?
-    @readouts = current_user.readouts.build(@quantities.map { |q| {quantity: q} })
+    @readouts = @quantities.map { |q| q.readouts.build }
 
     @user_units = current_user.units.ordered
 

app/controllers/units_controller.rb

@@ -17,7 +17,7 @@ class UnitsController < ApplicationController
   end
 
   def create
-    @unit = current_user.units.new(unit_params)
+    @unit = current_user.units.new(params.expect(Unit::ATTRIBUTES))
     if @unit.save
       @before = @unit.successive
       flash.now[:notice] = t('.success', unit: @unit)
@@ -30,7 +30,7 @@ class UnitsController < ApplicationController
   end
 
   def update
-    if @unit.update(unit_params.except(:base_id))
+    if @unit.update(params.except(:base_id).expect(Unit::ATTRIBUTES))
       flash.now[:notice] = t('.success', unit: @unit)
     else
       render :edit
@@ -40,11 +40,11 @@ class UnitsController < ApplicationController
   # TODO: Avoid double table width change by first un-hiding table header,
   # then displaying index, e.g. by re-displaying header in index
   def rebase
-    permitted = params.require(:unit).permit(:base_id)
-    permitted.merge!(multiplier: 1) if permitted[:base_id].blank? && @unit.multiplier != 1
+    unit_params = params.expect(unit: :base_id)
+    unit_params.merge!(multiplier: 1.0) if unit_params[:base_id].blank?
 
     @previous_base = @unit.base
-    @unit.update!(permitted)
+    @unit.update!(unit_params)
 
     @before = @unit.successive
     if @unit.multiplier_previously_changed?
@@ -59,10 +59,6 @@ class UnitsController < ApplicationController
 
   private
 
-  def unit_params
-    params.require(:unit).permit(Unit::ATTRIBUTES)
-  end
-
   def find_unit
     @unit = current_user.units.find_by!(id: params[:id])
   end

app/helpers/application_helper.rb

@@ -86,7 +86,6 @@ module ApplicationHelper
     def initialize(...)
       super(...)
       @default_options.merge!(@options.slice(:form))
-      @default_html_options.merge!(@options.slice(:form))
     end
 
     [:text_field, :password_field, :text_area].each do |selector|
@@ -104,15 +103,19 @@ module ApplicationHelper
     def number_field(method, options = {})
       attr_type = object.type_for_attribute(method)
       case attr_type.type
-      when :decimal
+      when :float, :double
         options[:value] = object.public_send(method)&.to_scientific
-        options[:step] ||= BigDecimal(10).power(-attr_type.scale)
-        options[:max] ||= BigDecimal(10).power(attr_type.precision - attr_type.scale) -
-          options[:step]
-        options[:min] = options[:min] == :step ? options[:step] : options[:min]
-        options[:min] ||= -options[:max]
-        options[:size] ||= attr_type.precision / 2
-      when :float
+        options[:step] ||= :any
+        options[:min] ||= Float::MIN_15
+        options[:max] ||= Float::MAX_15
+        # Longest possible number (written not using exponent):
+        #   sign (1), leading 0 (1), dot (1), exponent 0s (307), digits (15).
+        # This is only upper bound, which cannot guarantee the number won't fall
+        # out of range.
+        # TODO: add `[pattern]` to limit precision and (possibly) replace `[maxlength]`?
+        # NOTE: `[pattern]` is unavailable on `input[type=number]` and `[min]/[max]` is
+        # unavailable on `input[type=text]`.
+        options[:maxlength] ||= 3 + Float::MIN_10_EXP + Float::DIG
         options[:size] ||= 6
       end
       super
@@ -209,9 +212,7 @@ module ApplicationHelper
 
   def image_link_to_unless_current(name, image = nil, options = nil, html_options = {})
     name, html_options = link_or_button_options(:link, name, image, html_options)
-    # NOTE: Starting from Rails 8.1.0, below condition can be replaced with:
-    #   current_page?(options, method: [:get, :post])
-    if request.path == url_for(options)
+    if current_page?(options, method: [:get, :post])
       html_options = html_options.deep_merge DISABLED_ATTRIBUTES
     end
     link_to name, options, html_options

app/models/note.rb

@@ -0,0 +1,3 @@
+class Note < ApplicationRecord
+  ATTRIBUTES = [:text]
+end

app/models/quantity.rb

@@ -1,12 +1,12 @@
 class Quantity < ApplicationRecord
-  ATTRIBUTES = [:name, :description, :parent_id, :default_unit_id]
+  ATTRIBUTES = [:name, :description, :parent_id]
   attr_cached :depth, :pathname
 
   belongs_to :user, optional: true
   belongs_to :parent, optional: true, class_name: "Quantity"
-  belongs_to :default_unit, optional: true, class_name: "Unit"
   has_many :subquantities, ->{ order(:name) }, class_name: "Quantity",
     inverse_of: :parent, dependent: :restrict_with_error
+  has_many :readouts, dependent: :restrict_with_error
 
   validate if: ->{ parent.present? } do
     errors.add(:parent, :user_mismatch) unless user_id == parent.user_id

app/models/readout.rb

@@ -1,7 +1,9 @@
 class Readout < ApplicationRecord
-  ATTRIBUTES = [:quantity_id, :value, :unit_id, :taken_at]
+  ATTRIBUTES = [:quantity_id, :value, :unit_id]
 
   belongs_to :user
   belongs_to :quantity
   belongs_to :unit
+
+  # TODO: validate quantity.user_id == unit.user_id != NULL
 end

app/models/unit.rb

@@ -1,5 +1,5 @@
 class Unit < ApplicationRecord
-  ATTRIBUTES = [:symbol, :description, :multiplier, :base_id]
+  ATTRIBUTES = {unit: [:symbol, :description, :multiplier, :base_id]}
 
   belongs_to :user, optional: true
   belongs_to :base, optional: true, class_name: "Unit"
@@ -14,8 +14,8 @@ class Unit < ApplicationRecord
   validates :symbol, presence: true, uniqueness: {scope: :user_id},
     length: {maximum: type_for_attribute(:symbol).limit}
   validates :description, length: {maximum: type_for_attribute(:description).limit}
-  validates :multiplier, numericality: {equal_to: 1}, unless: :base
-  validates :multiplier, numericality: {greater_than: 0, precision: true, scale: true}, if: :base
+  validates :multiplier, numericality: {equal_to: 1.0}, unless: :base
+  validates :multiplier, numericality: {greater_than: 0.0}, if: :base
 
   scope :defaults, ->{ where(user: nil) }
   scope :defaults_diff, ->{
@@ -77,16 +77,14 @@ class Unit < ApplicationRecord
       .from(units).group(:base_id, :symbol)
   }
   scope :ordered, ->{
-    left_outer_joins(:base).order(ordering)
+    left_outer_joins(:base).order([
+      arel_table.coalesce(Arel::Table.new(:bases_units)[:symbol], arel_table[:symbol]),
+      arel_table[:base_id].not_eq(nil),
+      arel_table[:multiplier],
+      arel_table[:symbol]
+    ])
   }
 
-  def self.ordering
-    [arel_table.coalesce(Arel::Table.new(:bases_units)[:symbol], arel_table[:symbol]),
-     arel_table[:base_id].not_eq(nil),
-     :multiplier,
-     :symbol]
-  end
-
   before_destroy do
     # TODO: disallow destruction if any object depends on this unit
     nil
@@ -104,21 +102,21 @@ class Unit < ApplicationRecord
     user_id.nil?
   end
 
-  # Should only by invoked on Units returned from #defaults_diff which are #portable
+  # Should only by invoked on Units returned from #defaults_diff which are #portable.
   def port!(recipient)
     recipient_base = base && Unit.find_by!(symbol: base.symbol, user: recipient)
-    params = slice(ATTRIBUTES - [:symbol, :base_id])
+    params = slice(ATTRIBUTES[:unit] - [:symbol, :base_id])
     Unit.find_or_initialize_by(user: recipient, symbol: symbol)
       .update!(base: recipient_base, **params)
   end
 
   def successive
     units = Unit.arel_table
-    lead = Arel::Nodes::NamedFunction.new('LAG', [units[:id]])
-    window = Arel::Nodes::Window.new.order(*Unit.ordering)
-    lag_id = lead.over(window).as('lag_id')
-    Unit.with(
-      units: user.units.left_outer_joins(:base).select(units[Arel.star], lag_id)
-    ).where(units[:lag_id].eq(id)).first
+    Unit.with(units_with_lag: user.units.left_outer_joins(:base).select(
+      units[Arel.star],
+      Arel::Nodes::NamedFunction.new('LAG', [units[:id]])
+        .over(Arel::Nodes::Window.new.order(Unit.ordered.order_values)).as('lag_id')
+    )).from(Arel::Table.new(:units_with_lag).as(:units))
+      .where(units[:lag_id].eq(id)).take
   end
 end

app/views/measurements/_form.html.erb

@@ -8,7 +8,7 @@
         <tr class="italic">
           <td class="hexpand hmin50"><%= t '.taken_at_html' %></td>
           <td colspan="3" class="ralign">
-            <%= form.datetime_field :taken_at, required: true, value: Time.current.strftime('%Y-%m-%dT%H:%M') %>
+            <%= form.datetime_field :taken_at, required: true %>
           </td>
         </tr>
       <% end %>
@@ -33,7 +33,7 @@
   <div class="flex reverse">
     <%= form.button id: :create_measurement_button, disabled: true -%>
     <%= image_link_to t(:cancel), "close-outline", measurements_path, name: :cancel,
-      class: 'dangerous', onclick: render_turbo_stream('form_close') %>
+      class: 'auxiliary dangerous', onclick: render_turbo_stream('form_close') %>
   </div>
 <% end %>
 

app/views/quantities/_form.html.erb

@@ -8,11 +8,6 @@
     <td>
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
-    <td>
-      <%= form.collection_select :default_unit_id, @user_units, :id,
-        ->(u){ sanitize('&emsp;' * (u.base_id? ? 1 : 0) + u.symbol) },
-        {include_blank: true}, onchange: "this.dataset.changed = ''" %>
-    </td>
 
     <td class="flex">
       <%= form.button %>

app/views/quantities/_quantity.html.erb

@@ -10,7 +10,6 @@
       onclick: 'this.blur();', data: {turbo_stream: true} %>
   </td>
   <td><%= quantity.description %></td>
-  <td><%= quantity.default_unit&.symbol %></td>
 
   <% if current_user.at_least(:active) %>
     <td class="flex">

app/views/quantities/index.html.erb

@@ -16,7 +16,6 @@
     <tr>
       <th><%= Quantity.human_attribute_name(:name) %></th>
       <th class="hexpand"><%= Quantity.human_attribute_name(:description) %></th>
-      <th><%= Quantity.human_attribute_name(:default_unit) %></th>
       <% if current_user.at_least(:active) %>
         <th><%= t :actions %></th>
         <th></th>
@@ -26,7 +25,7 @@
                ondragover: "dragOver(event)", ondrop: "drop(event)",
                ondragenter: "dragEnter(event)", ondragleave: "dragLeave(event)",
                data: {drop_id: "quantity_", drop_id_param: "quantity[parent_id]"} do %>
-      <th colspan="5"><%= t '.top_level_drop' %></th>
+      <th colspan="4"><%= t '.top_level_drop' %></th>
     <% end %>
   </thead>
   <tbody id="quantities">

app/views/readouts/_form.html.erb

@@ -12,17 +12,10 @@
     <td>
       <%= form.collection_select :unit_id, @user_units, :id,
         ->(u){ sanitize('&emsp;' * (u.base_id ? 1 : 0) + u.symbol) },
-        {prompt: '', disabled: '', selected: readout.quantity.default_unit_id || ''}, required: true,
-        data: {default_unit_id: readout.quantity.default_unit_id || ''},
-        onchange: "readoutUnitChanged(this)" %>
+        {prompt: '', disabled: '', selected: ''}, required: true %>
     </td>
     <td class="flex">
       <%# TODO: change to _link_ after giving up displaying relative paths %>
-      <%= image_button_tag '', 'check-circle-outline',
-        class: 'set-default-unit', name: nil, type: 'button', disabled: true,
-        title: t('readouts.form.set_default_unit'),
-        data: {path: quantity_path(readout.quantity)},
-        onclick: 'setDefaultUnit(this)' %>
       <%= image_button_tag '', 'delete-outline', class: 'dangerous', name: nil,
         formaction: discard_readouts_path(readout.quantity),
         formmethod: :get, formnovalidate: true, data: {turbo_stream: true} %>

app/views/units/_form.html.erb

@@ -9,7 +9,7 @@
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
     <td>
-      <%= form.number_field :multiplier, required: true, size: 10, min: :step if @unit.base_id? %>
+      <%= form.number_field :multiplier, required: true if @unit.base_id? %>
     </td>
 
     <td class="flex">

app/views/units/_unit.html.erb

@@ -11,7 +11,7 @@
       data: {turbo_stream: true} %>
   </td>
   <td><%= unit.description %></td>
-  <td class="ralign"><%= unit.multiplier.to_html %></td>
+  <td class="ralign"><%= unit.multiplier.to_html if unit.base_id? %></td>
 
   <% if current_user.at_least(:active) %>
     <td class="flex">

app/views/units/rebase.turbo_stream.erb

@@ -1,4 +1,4 @@
 <%= turbo_stream.remove @unit %>
 <%= turbo_stream.replace @previous_base if @previous_base %>
-<%= turbo_stream.replace @unit.base if @unit.base_id? && (@previous_base.id != @unit.base_id) %>
+<%= turbo_stream.replace @unit.base if @unit.base_id? && (@previous_base&.id != @unit.base_id) %>
 <%= @before ? turbo_stream.before(@before, @unit) : turbo_stream.append(:units, @unit) %>

bin/ci

@@ -0,0 +1,6 @@
+#!/usr/bin/env ruby
+require_relative "../config/boot"
+require "active_support/continuous_integration"
+
+CI = ActiveSupport::ContinuousIntegration
+require_relative "../config/ci.rb"

bin/dev

@@ -0,0 +1,2 @@
+#!/usr/bin/env ruby
+exec "./bin/rails", "server", *ARGV

bin/setup

@@ -1,11 +1,10 @@
 #!/usr/bin/env ruby
 require "fileutils"
 
-# path to your application root.
 APP_ROOT = File.expand_path("..", __dir__)
 
 def system!(*args)
-  system(*args) || abort("\n== Command #{args} failed ==")
+  system(*args, exception: true)
 end
 
 FileUtils.chdir APP_ROOT do
@@ -14,7 +13,6 @@ FileUtils.chdir APP_ROOT do
   # Add necessary setup steps to this file.
 
   puts "== Installing dependencies =="
-  system! "gem install bundler --conservative"
   system("bundle check") || system!("bundle install")
 
   # puts "\n== Copying sample files =="
@@ -24,10 +22,14 @@ FileUtils.chdir APP_ROOT do
 
   puts "\n== Preparing database =="
   system! "bin/rails db:prepare"
+  system! "bin/rails db:reset" if ARGV.include?("--reset")
 
   puts "\n== Removing old logs and tempfiles =="
   system! "bin/rails log:clear tmp:clear"
 
-  puts "\n== Restarting application server =="
-  system! "bin/rails restart"
+  unless ARGV.include?("--skip-server")
+    puts "\n== Starting development server =="
+    STDOUT.flush # flush the output before exec(2) so that it displays
+    exec "bin/dev"
+  end
 end

config/application.rb.dist

@@ -18,14 +18,17 @@ require "rails/test_unit/railtie"
 # you've limited to :test, :development, or :production.
 Bundler.require(*Rails.groups)
 
+require_relative '../lib/default_settings_strategy'
+
 module FixinMe
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults 7.0
+    config.load_defaults 8.1
 
-    # Autoload lib/, required e.g. for core library extensions.
-    # https://guides.rubyonrails.org/autoloading_and_reloading_constants.html#config-autoload-lib-ignore.
-    config.autoload_lib(ignore: %w(assets tasks))
+    # Please, add to the `ignore` list any other `lib` subdirectories that do
+    # not contain `.rb` files, or that should not be reloaded or eager loaded.
+    # Common ones are `templates`, `generators`, or `middleware`, for example.
+    config.autoload_lib(ignore: %w[assets tasks])
 
     # Configuration for the application, engines, and railties goes here.
     #
@@ -38,16 +41,19 @@ module FixinMe
     config.action_dispatch.rescue_responses['ApplicationController::AccessForbidden'] = :forbidden
     config.action_dispatch.rescue_responses['ApplicationController::ParameterInvalid'] = :unprocessable_entity
 
+    # Set default migrations parameters.
+    config.active_record.migration_strategy = DefaultSettingsStrategy
+
     # SETUP: Below settings need to be updated on a per-installation basis.
     #
-    # URL to use in sent e-mails.
-    config.action_mailer.default_url_options = {host: 'localhost', :protocol => 'https'}
+    # Set host to be used by links generated in mailer templates.
+    config.action_mailer.default_url_options = {host: 'localhost', protocol: 'https'}
     # https://guides.rubyonrails.org/configuring.html#config-action-mailer-delivery-method
     config.action_mailer.delivery_method = :sendmail
 
     # List of hosts this app is available at.
     # https://guides.rubyonrails.org/configuring.html#actiondispatch-hostauthorization
-    config.hosts += ['localhost', 'example.com', IPAddr.new('1.2.3.4/32')]
+    config.hosts |= ['localhost']
 
     # Email address of admin account
     config.admin = 'admin@localhost'

config/ci.rb

@@ -0,0 +1,20 @@
+# Run using bin/ci
+
+CI.run do
+  step "Setup", "bin/setup --skip-server"
+
+  step "Security: Importmap vulnerability audit", "bin/importmap audit"
+  step "Tests: Rails", "bin/rails test"
+  step "Tests: Seeds", "env RAILS_ENV=test bin/rails db:seed:replant"
+
+  # Optional: Run system tests
+  # step "Tests: System", "bin/rails test:system"
+
+  # Optional: set a green GitHub commit status to unblock PR merge.
+  # Requires the `gh` CLI and `gh extension install basecamp/gh-signoff`.
+  # if success?
+  #   step "Signoff: All systems go. Ready for merge and deploy.", "gh signoff"
+  # else
+  #   failure "Signoff: CI failed. Do not merge or deploy.", "Fix the issues and try again."
+  # end
+end

config/database.yml.dist

@@ -24,27 +24,45 @@
 # Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
 # for a full overview on how database connection configuration can be specified.
 default: &default
-  adapter: mysql2
-  encoding: utf8mb4
-  collation: utf8mb4_0900_as_ci
-  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-  username: fixinme
-  password: Some-password1%
-  socket: /run/mysqld/mysqld.sock
+  pool: <%= ENV.fetch('RAILS_MAX_THREADS', 3) %>
+
+#mysql_default: &mysql_default
+#  <<: *default
+#  username: fixinme
+#  password: Some-password1%
+#  host: 127.0.0.1
+#  encoding: utf8mb4
+#  collation: utf8mb4_0900_as_ci
 
 production:
   <<: *default
-  database: fixinme
+  adapter: sqlite3
+  database: db/production.sqlite3
 
-# Unless you're planning on developing the application, you can skip
+# Unless you're planning on developing the application, you can skip/remove
 # configurations for development and test databases altogether.
 #development:
-#  <<: *default
+#  <<: *mysql_default
+#  adapter: mysql2
 #  database: fixinme_dev
 
-# Warning: The database defined as "test" will be erased and
+# Warning: The database(s) defined as "test" will be erased and
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 #test:
-#  <<: *default
+#  <<: *mysql_default
+#  adapter: mysql2
 #  database: fixinme_test
+
+# Multiple test databases can be provided. When more than one test db is
+# present, every test task (test, test:models, test:system, etc.) runs against
+# all of them.
+#test:
+#  mysql2:
+#    <<: *mysql_default
+#    adapter: mysql2
+#    database: fixinme_test
+#  sqlite3:
+#    <<: *default
+#    adapter: sqlite3
+#    database: db/test.sqlite3

config/environments/development.rb

@@ -3,10 +3,8 @@ require "active_support/core_ext/integer/time"
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
-  # In the development environment your application's code is reloaded any time
-  # it changes. This slows down response time but is perfect for development
-  # since you don't have to restart the web server when you make code changes.
-  config.cache_classes = false
+  # Make code changes take effect immediately without server restart.
+  config.enable_reloading = true
 
   # Do not eager load code on boot.
   config.eager_load = false
@@ -14,54 +12,52 @@ Rails.application.configure do
   # Show full error reports.
   config.consider_all_requests_local = true
 
-  # Enable server timing
+  # Enable server timing.
   config.server_timing = true
 
-  # Enable/disable caching. By default caching is disabled.
-  # Run rails dev:cache to toggle caching.
+  # Enable/disable Action Controller caching. By default Action Controller caching is disabled.
+  # Run rails dev:cache to toggle Action Controller caching.
   if Rails.root.join("tmp/caching-dev.txt").exist?
     config.action_controller.perform_caching = true
     config.action_controller.enable_fragment_cache_logging = true
-
-    config.cache_store = :memory_store
-    config.public_file_server.headers = {
-      "Cache-Control" => "public, max-age=#{2.days.to_i}"
-    }
+    config.public_file_server.headers = { "cache-control" => "public, max-age=#{2.days.to_i}" }
   else
     config.action_controller.perform_caching = false
-
-    config.cache_store = :null_store
   end
 
+  # Change to :null_store to avoid any caching.
+  config.cache_store = :memory_store
+
   # Don't care if the mailer can't send.
   config.action_mailer.raise_delivery_errors = false
 
+  # Make template changes take effect immediately.
   config.action_mailer.perform_caching = false
 
   # Print deprecation notices to the Rails logger.
   config.active_support.deprecation = :log
 
-  # Raise exceptions for disallowed deprecations.
-  config.active_support.disallowed_deprecation = :raise
-
-  # Tell Active Support which deprecation messages to disallow.
-  config.active_support.disallowed_deprecation_warnings = []
-
   # Raise an error on page load if there are pending migrations.
   config.active_record.migration_error = :page_load
 
   # Highlight code that triggered database queries in logs.
   config.active_record.verbose_query_logs = true
 
-  # Suppress logger output for asset requests.
-  config.assets.quiet = true
+  # Append comments with runtime information tags to SQL queries in logs.
+  config.active_record.query_log_tags_enabled = true
+
+  # Highlight code that enqueued background job in logs.
+  config.active_job.verbose_enqueue_logs = true
+
+  # Highlight code that triggered redirect in logs.
+  config.action_dispatch.verbose_redirect_logs = true
 
   # Raises error for missing translations.
   # config.i18n.raise_on_missing_translations = true
 
   # Annotate rendered view with file names.
-  # config.action_view.annotate_rendered_view_with_filenames = true
+  config.action_view.annotate_rendered_view_with_filenames = true
 
-  # Uncomment if you wish to allow Action Cable access from any origin.
-  # config.action_cable.disable_request_forgery_protection = true
+  # Raise error when a before_action's only/except options reference missing actions.
+  config.action_controller.raise_on_missing_callback_actions = true
 end

config/environments/production.rb

@@ -4,78 +4,83 @@ Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
   # Code is not reloaded between requests.
-  config.cache_classes = true
+  config.enable_reloading = false
 
-  # Eager load code on boot. This eager loads most of Rails and
-  # your application in memory, allowing both threaded web servers
-  # and those relying on copy on write to perform better.
-  # Rake tasks automatically ignore this option for performance.
+  # Eager load code on boot for better performance and memory savings (ignored by Rake tasks).
   config.eager_load = true
 
-  # Full error reports are disabled and caching is turned on.
-  config.consider_all_requests_local       = false
+  # Full error reports are disabled.
+  config.consider_all_requests_local = false
+
+  # Turn on fragment caching in view templates.
   config.action_controller.perform_caching = true
 
-  # Ensures that a master key has been made available in either ENV["RAILS_MASTER_KEY"]
-  # or in config/master.key. This key is used to decrypt credentials (and other encrypted files).
-  # config.require_master_key = true
-
-  # Disable serving static files from the `/public` folder by default since
-  # Apache or NGINX already handles this.
-  config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
-
-  # Compress CSS using a preprocessor.
-  # config.assets.css_compressor = :sass
-
-  # Do not fallback to assets pipeline if a precompiled asset is missed.
-  config.assets.compile = false
+  # Cache assets for far-future expiry since they are all digest stamped.
+  config.public_file_server.headers = { "cache-control" => "public, max-age=#{1.year.to_i}" }
 
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.asset_host = "http://assets.example.com"
 
-  # Specifies the header that your server uses for sending files.
-  # config.action_dispatch.x_sendfile_header = "X-Sendfile" # for Apache
-  # config.action_dispatch.x_sendfile_header = "X-Accel-Redirect" # for NGINX
+  # Assume all access to the app is happening through a SSL-terminating reverse proxy.
+  config.assume_ssl = true
 
   # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
-  # config.force_ssl = true
+  config.force_ssl = true
 
-  # Include generic and useful information about system operation, but avoid logging too much
-  # information to avoid inadvertent exposure of personally identifiable information (PII).
-  config.log_level = :info
+  # Skip http-to-https redirect for the default health check endpoint.
+  # config.ssl_options = { redirect: { exclude: ->(request) { request.path == "/up" } } }
 
-  # Prepend all log lines with the following tags.
+  # Log to STDOUT with the current request id as a default log tag.
   config.log_tags = [ :request_id ]
+  config.logger   = ActiveSupport::TaggedLogging.logger(STDOUT)
 
-  # Use a different cache store in production.
+  # Change to "debug" to log everything (including potentially personally-identifiable information!).
+  config.log_level = ENV.fetch("RAILS_LOG_LEVEL", "info")
+
+  # Prevent health checks from clogging up the logs.
+  config.silence_healthcheck_path = "/up"
+
+  # Don't log any deprecations.
+  config.active_support.report_deprecations = false
+
+  # Replace the default in-process memory cache store with a durable alternative.
   # config.cache_store = :mem_cache_store
 
-  config.action_mailer.perform_caching = false
+  # Replace the default in-process and non-durable queuing backend for Active Job.
+  # config.active_job.queue_adapter = :resque
 
   # Ignore bad email addresses and do not raise email delivery errors.
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.
   # config.action_mailer.raise_delivery_errors = false
 
+  # Specify outgoing SMTP server. Remember to add smtp/* credentials via bin/rails credentials:edit.
+  # config.action_mailer.smtp_settings = {
+  #   user_name: Rails.application.credentials.dig(:smtp, :user_name),
+  #   password: Rails.application.credentials.dig(:smtp, :password),
+  #   address: "smtp.example.com",
+  #   port: 587,
+  #   authentication: :plain
+  # }
+
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation cannot be found).
   config.i18n.fallbacks = true
 
-  # Don't log any deprecations.
-  config.active_support.report_deprecations = false
-
-  # Use default logging formatter so that PID and timestamp are not suppressed.
-  config.log_formatter = ::Logger::Formatter.new
-
-  # Use a different logger for distributed setups.
-  # require "syslog/logger"
-  # config.logger = ActiveSupport::TaggedLogging.new(Syslog::Logger.new "app-name")
-
-  if ENV["RAILS_LOG_TO_STDOUT"].present?
-    logger           = ActiveSupport::Logger.new(STDOUT)
-    logger.formatter = config.log_formatter
-    config.logger    = ActiveSupport::TaggedLogging.new(logger)
-  end
-
   # Do not dump schema after migrations.
   config.active_record.dump_schema_after_migration = false
+
+  # Only use :id for inspections in production.
+  config.active_record.attributes_for_inspect = [ :id ]
+
+  # Enable DNS rebinding protection and other `Host` header attacks.
+  # config.hosts = [
+  #   "example.com",     # Allow requests from example.com
+  #   /.*\.example\.com/ # Allow requests from subdomains like `www.example.com`
+  # ]
+  #
+  # Skip DNS rebinding protection for the default health check endpoint.
+  # config.host_authorization = { exclude: ->(request) { request.path == "/up" } }
+
+  # Protect e-mail addresses from being logged only in production.
+  config.filter_parameters += [:email]
 end

config/environments/test.rb

@@ -1,5 +1,3 @@
-require "active_support/core_ext/integer/time"
-
 # The test environment is used exclusively to run your application's
 # test suite. You never need to work with it otherwise. Remember that
 # your test database is "scratch space" for the test suite and is wiped
@@ -8,57 +6,49 @@ require "active_support/core_ext/integer/time"
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
-  # Turn false under Spring and add config.action_view.cache_template_loading = true.
-  config.cache_classes = true
+  # While tests run files are not watched, reloading is not necessary.
+  config.enable_reloading = false
 
-  # Eager loading loads your whole application. When running a single test locally,
-  # this probably isn't necessary. It's a good idea to do in a continuous integration
-  # system, or in some way before deploying your code.
+  # Eager loading loads your entire application. When running a single test locally,
+  # this is usually not necessary, and can slow down your test suite. However, it's
+  # recommended that you enable it in continuous integration systems to ensure eager
+  # loading is working properly before deploying your code.
   config.eager_load = ENV["CI"].present?
 
-  # Configure public file server for tests with Cache-Control for performance.
-  config.public_file_server.enabled = true
-  config.public_file_server.headers = {
-    "Cache-Control" => "public, max-age=#{1.hour.to_i}"
-  }
+  # Configure public file server for tests with cache-control for performance.
+  config.public_file_server.headers = { "cache-control" => "public, max-age=3600" }
 
-  # Hide full error reports.
-  config.consider_all_requests_local     = false
-  # Render exception templates instead of raising exceptions.
-  config.action_dispatch.show_exceptions = :all
+  # Behave as in `production`.
+  config.consider_all_requests_local = false
 
-  # Disable caching.
-  config.action_controller.perform_caching = false
   config.cache_store = :null_store
 
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false
 
-  config.action_mailer.perform_caching = false
-
   # Tell Action Mailer not to deliver emails to the real world.
   # The :test delivery method accumulates sent emails in the
   # ActionMailer::Base.deliveries array.
   config.action_mailer.delivery_method = :test
-  config.action_mailer.default_url_options = {host: '127.0.0.1', :protocol => 'http'}
+
+  # Set host to be used by links generated in mailer templates.
+  config.action_mailer.default_url_options = {host: Capybara.server_host,
+                                              protocol: 'http'}
 
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
-  # Raise exceptions for disallowed deprecations.
-  config.active_support.disallowed_deprecation = :raise
-
-  # Tell Active Support which deprecation messages to disallow.
-  config.active_support.disallowed_deprecation_warnings = []
-
   # Raises error for missing translations.
   config.i18n.raise_on_missing_translations = true
 
   # Annotate rendered view with file names.
   # config.action_view.annotate_rendered_view_with_filenames = true
 
-  config.log_level = :info
+  # Raise error when a before_action's only/except options reference missing actions.
+  config.action_controller.raise_on_missing_callback_actions = true
 
-  # Allow Capybara's dynamic test server host (127.0.0.1:<random_port>)
-  config.hosts << '127.0.0.1'
+  # Allow Capybara application server IP
+  config.hosts |= [IPAddr.new(Capybara.server_host)]
+
+  config.log_level = :info
 end

config/initializers/assets.rb

@@ -5,8 +5,3 @@ Rails.application.config.assets.version = "1.0"
 
 # Add additional assets to the asset load path.
 # Rails.application.config.assets.paths << Emoji.images_path
-
-# Precompile additional assets.
-# application.js, application.css, and all non-JS/CSS in the app/assets
-# folder are already added.
-Rails.application.config.assets.precompile += %w( '*.svg' )

config/initializers/content_security_policy.rb

@@ -16,9 +16,13 @@
 #     # policy.report_uri "/csp-violation-report-endpoint"
 #   end
 #
-#   # Generate session nonces for permitted importmap and inline scripts
+#   # Generate session nonces for permitted importmap, inline scripts, and inline styles.
 #   config.content_security_policy_nonce_generator = ->(request) { request.session.id.to_s }
-#   config.content_security_policy_nonce_directives = %w(script-src)
+#   config.content_security_policy_nonce_directives = %w(script-src style-src)
+#
+#   # Automatically add `nonce` to `javascript_tag`, `javascript_include_tag`, and `stylesheet_link_tag`
+#   # if the corresponding directives are specified in `content_security_policy_nonce_directives`.
+#   # config.content_security_policy_nonce_auto = true
 #
 #   # Report violations without enforcing the policy.
 #   # config.content_security_policy_report_only = true

config/initializers/core_ext.rb

@@ -1,5 +1,6 @@
 require 'core_ext/array_delete_bang'
-require 'core_ext/big_decimal_scientific_notation'
+require 'core_ext/float'
+require 'core_ext/range'
 
 ActiveSupport.on_load :action_dispatch_system_test_case do
   prepend CoreExt::ActionDispatch::SystemTesting::TestHelpers::ScreenshotHelperUniqueId
@@ -10,9 +11,6 @@ ActiveSupport.on_load :action_view do
 end
 
 ActiveSupport.on_load :active_record do
-  ActiveModel::Validations::NumericalityValidator
-    .prepend CoreExt::ActiveModel::Validations::NumericalityValidatesPrecisionAndScale
-
   # Temporary patch for https://github.com/rails/rails/pull/54658
   Arel::TreeManager::StatementMethods
     .prepend CoreExt::Arel::TreeManager::StatementMethodsCteUpdateAndDelete

config/initializers/devise.rb

@@ -179,7 +179,7 @@ Devise.setup do |config|
 
   # ==> Configuration for :validatable
   # Range for password length.
-  config.password_length = 5..128
+  config.password_length = 5..32
 
   # Email regex used to validate email formats. It simply asserts that
   # one (and only one) @ exists in the given string. This is mainly

config/initializers/filter_parameter_logging.rb

@@ -1,8 +1,8 @@
 # Be sure to restart your server when you modify this file.
 
-# Configure parameters to be filtered from the log file. Use this to limit dissemination of
-# sensitive information. See the ActiveSupport::ParameterFilter documentation for supported
-# notations and behaviors.
+# Configure parameters to be partially matched (e.g. passw matches password) and filtered from the log file.
+# Use this to limit dissemination of sensitive information.
+# See the ActiveSupport::ParameterFilter documentation for supported notations and behaviors.
 Rails.application.config.filter_parameters += [
-  :passw, :secret, :token, :_key, :crypt, :salt, :certificate, :otp, :ssn
+  :passw, :secret, :token, :_key, :crypt, :salt, :certificate, :otp, :ssn, :cvv, :cvc
 ]

config/locales/en.yml

@@ -4,20 +4,11 @@ en:
       # Format contains non-breaking space: 160.chr(Encoding::UTF_8)
       default: "%Y-%m-%d %H:%M %Z"
       without_tz: "%Y-%m-%d %H:%M"
-  errors:
-    messages:
-      precision_exceeded: must not exceed %{value} significant digits
-      scale_exceeded: must not exceed %{value} decimal digits
   activerecord:
     attributes:
       quantity:
-        default_unit: Default unit
         description: Description
         name: Name
-      readout:
-        created_at: Recorded at
-        taken_at: Taken at
-        value: Value
       unit:
         base: Base unit
         description: Description
@@ -86,9 +77,6 @@ en:
       revert: Revert
       sign_out: Sign out
       source_code: Get code
-  readouts:
-    form:
-      set_default_unit: Set as default unit
   measurements:
     navigation: Measurements
     no_items: There are no measurements taken. You can Add some now.
@@ -97,15 +85,6 @@ en:
       taken_at_html: Measurement taken at 
     index:
       new_measurement: Add measurement
-    readout:
-      destroy: Delete
-    create:
-      success:
-        one: Recorded 1 measurement.
-        other: Recorded %{count} measurements.
-      no_readouts: No readouts selected.
-    destroy:
-      success: Measurement deleted.
   quantities:
     navigation: Quantities
     no_items: There are no configured quantities. You can Add some or Import from defaults.

config/puma.rb.dist

@@ -1,43 +1,41 @@
-# Puma can serve each request in a thread from an internal thread pool.
-# The `threads` method setting takes two numbers: a minimum and maximum.
-# Any libraries that use thread pools should be configured to match
-# the maximum value specified for Puma. Default is set to 5 threads for minimum
-# and maximum; this matches the default thread size of Active Record.
+# This configuration file will be evaluated by Puma. The top-level methods that
+# are invoked here are part of Puma's configuration DSL. For more information
+# about methods provided by the DSL, see https://puma.io/puma/Puma/DSL.html.
 #
-max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
-min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
-threads min_threads_count, max_threads_count
-
-# Specifies the `worker_timeout` threshold that Puma will use to wait before
-# terminating a worker in development environments.
+# Puma starts a configurable number of processes (workers) and each process
+# serves each request in a thread from an internal thread pool.
 #
-worker_timeout 3600 if ENV.fetch("RAILS_ENV", "development") == "development"
+# You can control the number of workers using ENV["WEB_CONCURRENCY"]. You
+# should only set this value when you want to run 2 or more workers. The
+# default is already 1.
+#
+# The ideal number of threads per worker depends both on how much time the
+# application spends waiting for IO operations and on how much you wish to
+# prioritize throughput over latency.
+#
+# As a rule of thumb, increasing the number of threads will increase how much
+# traffic a given process can handle (throughput), but due to CRuby's
+# Global VM Lock (GVL) it has diminishing returns and will degrade the
+# response time (latency) of the application.
+#
+# The default is set to 3 threads as it's deemed a decent compromise between
+# throughput and latency for the average Rails application.
+#
+# Any libraries that use a connection pool or another resource pool should
+# be configured to provide at least as many connections as the number of
+# threads. This includes Active Record's `pool` parameter in `database.yml`.
+threads_count = ENV.fetch("RAILS_MAX_THREADS", 3)
+threads threads_count, threads_count
 
 # Specifies the `port` that Puma will listen on to receive requests; default is 3000.
-#
-port ENV.fetch("PORT") { 3000 }
-
-# Specifies the `environment` that Puma will run in.
-#
-environment ENV.fetch("RAILS_ENV") { "development" }
-
-# Specifies the `pidfile` that Puma will use.
-pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
-
-# Specifies the number of `workers` to boot in clustered mode.
-# Workers are forked web server processes. If using threads and workers together
-# the concurrency of the application would be max `threads` * `workers`.
-# Workers do not work on JRuby or Windows (both of which do not support
-# processes).
-#
-# workers ENV.fetch("WEB_CONCURRENCY") { 2 }
-
-# Use the `preload_app!` method when specifying a `workers` number.
-# This directive tells Puma to first boot the application and load code
-# before forking the application. This takes advantage of Copy On Write
-# process behavior so workers use less memory.
-#
-# preload_app!
+port ENV.fetch("PORT", 3000), '127.0.0.1'
 
 # Allow puma to be restarted by `bin/rails restart` command.
 plugin :tmp_restart
+
+# Run the Solid Queue supervisor inside of Puma for single-server deployments
+plugin :solid_queue if ENV["SOLID_QUEUE_IN_PUMA"]
+
+# Specify the PID file. Defaults to tmp/pids/server.pid in development.
+# In other environments, only set the PID file if requested.
+pidfile ENV["PIDFILE"] if ENV["PIDFILE"]

config/routes.rb

@@ -15,7 +15,10 @@ Rails.application.routes.draw do
 
   namespace :default do
     resources :units, only: [:index, :destroy] do
-      member { post :import, :export }
+      member {
+        post :import
+        post :export
+      }
       #collection { post :import_all }
     end
   end

db/migrate/20230309185340_create_users.rb

@@ -1,11 +1,11 @@
-class CreateUsers < ActiveRecord::Migration[7.0]
+class CreateUsers < ActiveRecord::Migration[8.1]
   def change
     create_table :users do |t|
       t.string :email, null: false, limit: 64
       t.integer :status, null: false, default: 0
 
-      t.timestamps null: false
+      t.timestamps
     end
-    add_index :users, :email, unique: true
+    add_index :users, :email
   end
 end

db/migrate/20230311220654_add_devise_to_users.rb

@@ -1,4 +1,4 @@
-class AddDeviseToUsers < ActiveRecord::Migration[7.0]
+class AddDeviseToUsers < ActiveRecord::Migration[8.1]
   def change
     change_table :users do |t|
       ## NOTE: commented fields left for reference/inclusion in future migrations
@@ -34,8 +34,8 @@ class AddDeviseToUsers < ActiveRecord::Migration[7.0]
       # t.integer :failed_attempts, default: 0, null: false 
     end
 
-    add_index :users, :reset_password_token, unique: true
-    add_index :users, :confirmation_token, unique: true
+    add_index :users, :reset_password_token
+    add_index :users, :confirmation_token
     # add_index :users, :unlock_token, unique: true
   end
 end

db/migrate/20230602185352_create_units.rb

@@ -1,14 +1,15 @@
-class CreateUnits < ActiveRecord::Migration[7.0]
+class CreateUnits < ActiveRecord::Migration[8.1]
   def change
     create_table :units do |t|
-      t.references :user, foreign_key: true
+      t.references :user, foreign_key: {on_delete: :cascade}
       t.string :symbol, null: false, limit: 15
       t.text :description
-      t.decimal :multiplier, null: false, precision: 30, scale: 15, default: 1.0
+      t.float :multiplier, null: false, limit: Float::MANT_DIG, default: 1.0
       t.references :base, foreign_key: {to_table: :units, on_delete: :cascade}
 
-      t.timestamps null: false
+      t.timestamps
     end
-    add_index :units, [:user_id, :symbol], unique: true
+    add_index :units, [:user_id, :symbol]
+    add_index :units, [:id, :user_id]
   end
 end

db/migrate/20250104194343_create_quantities.rb

@@ -1,17 +1,18 @@
-class CreateQuantities < ActiveRecord::Migration[7.2]
+class CreateQuantities < ActiveRecord::Migration[8.1]
   def change
     create_table :quantities do |t|
-      t.references :user, foreign_key: true
+      t.references :user, foreign_key: {on_delete: :cascade}
       t.string :name, null: false, limit: 31
       t.text :description
       t.references :parent, foreign_key: {to_table: :quantities, on_delete: :cascade}
 
-      t.timestamps null: false
+      t.timestamps
 
       # Caches; can be computed from other attributes
       t.integer :depth, null: false, default: 0
       t.string :pathname, null: false, limit: 511
     end
-    add_index :quantities, [:user_id, :parent_id, :name], unique: true
+    add_index :quantities, [:user_id, :parent_id, :name]
+    add_index :quantities, [:id, :user_id]
   end
 end

db/migrate/20250121230456_create_readouts.rb

@@ -1,19 +1,69 @@
-class CreateReadouts < ActiveRecord::Migration[7.2]
+class CreateReadouts < ActiveRecord::Migration[8.1]
   def change
-    create_table :readouts do |t|
-      # Reference :user through :quantity (:measurement may be NULL).
-      t.references :measurement, foreign_key: true
-      t.references :quantity, null: false, foreign_key: true
-      # :category + :value + :unit as a separate table? (NumericValue, TextValue)
-      t.integer :category, null: false, default: 0
-      t.float :value, null: false, limit: Float::MANT_DIG
-      t.references :unit, foreign_key: true
-      # Move to Measurement?
+    create_table :notes do |t|
+      t.text :text, null: false
+
+      t.timestamps
+    end
+
+    create_table :measurements do |t|
+      t.datetime :taken_at, null: false
       #t.references :collector, foreign_key: true
       #t.references :device, foreign_key: true
+      t.references :note, foreign_key: {on_delete: :nullify}
 
-      t.timestamps null: false
+      t.timestamps
     end
-    add_index :readouts, [:quantity_id, :created_at], unique: true
+    add_index :measurements, :taken_at
+
+    # Defining Readouts as a super-/subclass polymorphic relations for different
+    # subclass data types (numeric, string, file) is not possible with proper
+    # referential integrity constraints. The required constraints are:
+    # * for every subclass record to have superclass record,
+    # * for every superclass record to have only one type of subclass record,
+    # * for every superclass record to have subclass record (unenforcable).
+    #   * this can be partially remedied by making superlass an abstract class in
+    #     Rails and disallow direct creation of records, but direct data
+    #     manipulation can still break referential integrity.
+    # Defining separate {Numeric,Text,File}_Readouts tables would make the
+    # unique index constraint unenforcable.
+    create_table :readouts do |t|
+      t.references :user, null: false, foreign_key: {on_delete: :cascade}
+      t.references :measurement, foreign_key: {on_delete: :cascade}
+      t.references :quantity, null: false, foreign_key: {on_delete: :cascade}
+      t.integer :category, null: false, default: 0
+      t.float :value, null: false, limit: Float::MANT_DIG
+      t.references :unit, null: false, foreign_key: {on_delete: :cascade}
+      # TODO: consider additional columns to allow wider range of value types
+      # t.text :text
+      # t.datetime :time
+      # t.references :file
+      # Possibly mutually exclusive with :unit or check constraint for:
+      #   :unit is not null <=> :value is not null
+
+      t.timestamps
+    end
+    add_index :readouts, [:measurement_id, :quantity_id, :category]
+    add_foreign_key :readouts, :quantities, column: [:quantity_id, :user_id],
+      primary_key: [:id, :user_id]
+    add_foreign_key :readouts, :units, column: [:unit_id, :user_id],
+      primary_key: [:id, :user_id]
+
+    # TODO: remove below tables after current setup verified
+    #create_table :numeric_values do |t|
+    #  t.references :readout, null: false, foreign_key: {on_delete: :cascade}
+    #  t.float :value, null: false, limit: Float::MANT_DIG
+    #  t.references :unit, null: false, foreign_key: {on_delete: :cascade}
+    #  # + generated, not stored column :value_type
+    #  # + foreign key constraint to readouts: [:readout_id, :value_id, :value_type]
+    #  # or 2 constraints: [:readout_id, :value_id], [:value_id, :value_type]
+    #  # if readouts.value_id needed, otherwise just one constraint:
+    #  # [:readout_id, :value_type]
+    #end
+
+    #create_table :string_values do |t|
+    #  t.references :readout, null: false, foreign_key: {on_delete: :cascade}
+    #  t.string :value, null: false, limit: 32
+    #end
   end
 end

db/migrate/20260402000000_add_taken_at_to_readouts.rb

@@ -1,6 +0,0 @@
-class AddTakenAtToReadouts < ActiveRecord::Migration[7.2]
-  def change
-    add_column :readouts, :taken_at, :datetime
-    add_index :readouts, [:user_id, :taken_at]
-  end
-end

db/migrate/20260403000000_add_default_unit_to_quantities.rb

@@ -1,5 +0,0 @@
-class AddDefaultUnitToQuantities < ActiveRecord::Migration[7.2]
-  def change
-    add_reference :quantities, :default_unit, foreign_key: {to_table: :units}, null: true
-  end
-end

db/schema.rb

@@ -10,7 +10,22 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2026_04_03_000000) do
+ActiveRecord::Schema[8.1].define(version: 2025_01_21_230456) do
+  create_table "measurements", charset: "utf8mb4", collation: "utf8mb4_0900_as_ci", force: :cascade do |t|
+    t.datetime "taken_at", null: false
+    t.bigint "note_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["note_id"], name: "index_measurements_on_note_id"
+    t.index ["taken_at"], name: "index_measurements_on_taken_at", unique: true
+  end
+
+  create_table "notes", charset: "utf8mb4", collation: "utf8mb4_0900_as_ci", force: :cascade do |t|
+    t.text "text", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+
   create_table "quantities", charset: "utf8mb4", collation: "utf8mb4_0900_as_ci", force: :cascade do |t|
     t.bigint "user_id"
     t.string "name", limit: 31, null: false
@@ -20,8 +35,7 @@ ActiveRecord::Schema[7.2].define(version: 2026_04_03_000000) do
     t.datetime "updated_at", null: false
     t.integer "depth", default: 0, null: false
     t.string "pathname", limit: 511, null: false
-    t.bigint "default_unit_id"
-    t.index ["default_unit_id"], name: "index_quantities_on_default_unit_id"
+    t.index ["id", "user_id"], name: "index_quantities_on_id_and_user_id", unique: true
     t.index ["parent_id"], name: "index_quantities_on_parent_id"
     t.index ["user_id", "parent_id", "name"], name: "index_quantities_on_user_id_and_parent_id_and_name", unique: true
     t.index ["user_id"], name: "index_quantities_on_user_id"
@@ -29,28 +43,32 @@ ActiveRecord::Schema[7.2].define(version: 2026_04_03_000000) do
 
   create_table "readouts", charset: "utf8mb4", collation: "utf8mb4_0900_as_ci", force: :cascade do |t|
     t.bigint "user_id", null: false
+    t.bigint "measurement_id"
     t.bigint "quantity_id", null: false
-    t.bigint "unit_id"
-    t.decimal "value", precision: 30, scale: 15, null: false
+    t.integer "category", default: 0, null: false
+    t.float "value", limit: 53, null: false
+    t.bigint "unit_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.datetime "taken_at"
-    t.index ["quantity_id", "created_at"], name: "index_readouts_on_quantity_id_and_created_at", unique: true
+    t.index ["measurement_id", "quantity_id", "category"], name: "index_readouts_on_measurement_id_and_quantity_id_and_category", unique: true
+    t.index ["measurement_id"], name: "index_readouts_on_measurement_id"
+    t.index ["quantity_id", "user_id"], name: "fk_rails_9d92eaafc6"
     t.index ["quantity_id"], name: "index_readouts_on_quantity_id"
+    t.index ["unit_id", "user_id"], name: "fk_rails_348b0fb4c5"
     t.index ["unit_id"], name: "index_readouts_on_unit_id"
     t.index ["user_id"], name: "index_readouts_on_user_id"
-    t.index ["user_id", "taken_at"], name: "index_readouts_on_user_id_and_taken_at"
   end
 
   create_table "units", charset: "utf8mb4", collation: "utf8mb4_0900_as_ci", force: :cascade do |t|
     t.bigint "user_id"
     t.string "symbol", limit: 15, null: false
     t.text "description"
-    t.decimal "multiplier", precision: 30, scale: 15, default: "1.0", null: false
+    t.float "multiplier", limit: 53, default: 1.0, null: false
     t.bigint "base_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["base_id"], name: "index_units_on_base_id"
+    t.index ["id", "user_id"], name: "index_units_on_id_and_user_id", unique: true
     t.index ["user_id", "symbol"], name: "index_units_on_user_id_and_symbol", unique: true
     t.index ["user_id"], name: "index_units_on_user_id"
   end
@@ -73,12 +91,15 @@ ActiveRecord::Schema[7.2].define(version: 2026_04_03_000000) do
     t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
   end
 
+  add_foreign_key "measurements", "notes", on_delete: :nullify
   add_foreign_key "quantities", "quantities", column: "parent_id", on_delete: :cascade
-  add_foreign_key "quantities", "units", column: "default_unit_id"
-  add_foreign_key "quantities", "users"
-  add_foreign_key "readouts", "quantities"
-  add_foreign_key "readouts", "units"
-  add_foreign_key "readouts", "users"
+  add_foreign_key "quantities", "users", on_delete: :cascade
+  add_foreign_key "readouts", "measurements", on_delete: :cascade
+  add_foreign_key "readouts", "quantities", column: ["quantity_id", "user_id"], primary_key: ["id", "user_id"]
+  add_foreign_key "readouts", "quantities", on_delete: :cascade
+  add_foreign_key "readouts", "units", column: ["unit_id", "user_id"], primary_key: ["id", "user_id"]
+  add_foreign_key "readouts", "units", on_delete: :cascade
+  add_foreign_key "readouts", "users", on_delete: :cascade
   add_foreign_key "units", "units", column: "base_id", on_delete: :cascade
-  add_foreign_key "units", "users"
+  add_foreign_key "units", "users", on_delete: :cascade
 end

db/seeds.rb

@@ -7,17 +7,21 @@
 User.transaction do
   break if User.find_by status: :admin
 
-  User.create! email: Rails.configuration.admin, password: 'admin', status: :admin do |user|
+  email = Rails.configuration.admin
+  password_length = SecureRandom.rand(Rails.configuration.devise.password_length)
+  password = SecureRandom.alphanumeric(password_length)
+
+  User.create!(email: email, password: password, status: :admin) do |user|
     user.skip_confirmation!
-    print "Creating #{user.status} account '#{user.email}' with password '#{user.password}'..."
+    print "Creating #{user.status} account '#{user.email}'" \
+      " with password '#{user.password}'..."
   end
   puts "done."
-
 rescue ActiveRecord::RecordInvalid => exception
-  puts "failed. #{exception.message}"
+  puts "failed.", exception.message
 end
 
 # Formulas will be deleted as dependent on Quantities
 #[Source, Quantity, Unit].each { |model| model.defaults.delete_all }
 
-require_relative 'seeds/units.rb'
+load "db/seeds/units.rb"

db/seeds/templates/units.erb

@@ -4,7 +4,7 @@ Unit.transaction do
 <% Unit.defaults.ordered.each do |unit| %>
 <%= "\n" if unit.base.nil? %>
   units['<%= unit.symbol %>'] =
-    Unit.create symbol: '<%= unit.symbol %>',<% unless unit.base.nil? %> base: units['<%= unit.base.symbol %>'], multiplier: '<%= unit.multiplier.to_scientific %>',<% end %>
+    Unit.create symbol: '<%= unit.symbol %>',<% if unit.base_id? %> base: units['<%= unit.base.symbol %>'], multiplier: '<%= unit.multiplier.to_scientific %>',<% end %>
                 description: '<%= unit.description %>'
 <% end %>
 end

db/sqlite3_schema.rb

@@ -0,0 +1,103 @@
+# This file is auto-generated from the current state of the database. Instead
+# of editing this file, please use the migrations feature of Active Record to
+# incrementally modify your database, and then regenerate this schema definition.
+#
+# This file is the source Rails uses to define your schema when running `bin/rails
+# db:schema:load`. When creating a new database, `bin/rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
+#
+# It's strongly recommended that you check this file into your version control system.
+
+ActiveRecord::Schema[8.1].define(version: 2025_01_21_230456) do
+  create_table "measurements", force: :cascade do |t|
+    t.datetime "taken_at", null: false
+    t.integer "note_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["note_id"], name: "index_measurements_on_note_id"
+    t.index ["taken_at"], name: "index_measurements_on_taken_at", unique: true
+  end
+
+  create_table "notes", force: :cascade do |t|
+    t.text "text", limit: 65535, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+
+  create_table "quantities", force: :cascade do |t|
+    t.integer "user_id"
+    t.string "name", limit: 31, null: false
+    t.text "description", limit: 65535
+    t.integer "parent_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.integer "depth", default: 0, null: false
+    t.string "pathname", limit: 511, null: false
+    t.index ["id", "user_id"], name: "index_quantities_on_id_and_user_id", unique: true
+    t.index ["parent_id"], name: "index_quantities_on_parent_id"
+    t.index ["user_id", "parent_id", "name"], name: "index_quantities_on_user_id_and_parent_id_and_name", unique: true
+    t.index ["user_id"], name: "index_quantities_on_user_id"
+  end
+
+  create_table "readouts", force: :cascade do |t|
+    t.integer "user_id", null: false
+    t.integer "measurement_id"
+    t.integer "quantity_id", null: false
+    t.integer "category", default: 0, null: false
+    t.float "value", limit: 53, null: false
+    t.integer "unit_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["measurement_id", "quantity_id", "category"], name: "index_readouts_on_measurement_id_and_quantity_id_and_category", unique: true
+    t.index ["measurement_id"], name: "index_readouts_on_measurement_id"
+    t.index ["quantity_id"], name: "index_readouts_on_quantity_id"
+    t.index ["unit_id"], name: "index_readouts_on_unit_id"
+    t.index ["user_id"], name: "index_readouts_on_user_id"
+  end
+
+  create_table "units", force: :cascade do |t|
+    t.integer "user_id"
+    t.string "symbol", limit: 15, null: false
+    t.text "description", limit: 65535
+    t.float "multiplier", limit: 53, default: 1.0, null: false
+    t.integer "base_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["base_id"], name: "index_units_on_base_id"
+    t.index ["id", "user_id"], name: "index_units_on_id_and_user_id", unique: true
+    t.index ["user_id", "symbol"], name: "index_units_on_user_id_and_symbol", unique: true
+    t.index ["user_id"], name: "index_units_on_user_id"
+  end
+
+  create_table "users", force: :cascade do |t|
+    t.string "email", limit: 64, null: false
+    t.integer "status", default: 0, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.string "encrypted_password", default: "", null: false
+    t.string "reset_password_token"
+    t.datetime "reset_password_sent_at"
+    t.datetime "remember_created_at"
+    t.string "confirmation_token"
+    t.datetime "confirmed_at"
+    t.datetime "confirmation_sent_at"
+    t.string "unconfirmed_email", limit: 64
+    t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
+    t.index ["email"], name: "index_users_on_email", unique: true
+    t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
+  end
+
+  add_foreign_key "measurements", "notes", on_delete: :nullify
+  add_foreign_key "quantities", "quantities", column: "parent_id", on_delete: :cascade
+  add_foreign_key "quantities", "users", on_delete: :cascade
+  add_foreign_key "readouts", "measurements", on_delete: :cascade
+  add_foreign_key "readouts", "quantities", column: ["quantity_id", "user_id"], primary_key: ["id", "user_id"]
+  add_foreign_key "readouts", "quantities", on_delete: :cascade
+  add_foreign_key "readouts", "units", column: ["unit_id", "user_id"], primary_key: ["id", "user_id"]
+  add_foreign_key "readouts", "units", on_delete: :cascade
+  add_foreign_key "readouts", "users", on_delete: :cascade
+  add_foreign_key "units", "units", column: "base_id", on_delete: :cascade
+  add_foreign_key "units", "users", on_delete: :cascade
+end

lib/core_ext/active_model/validations/numericality_validates_precision_and_scale.rb

@@ -1,19 +0,0 @@
-module CoreExt::ActiveModel::Validations::NumericalityValidatesPrecisionAndScale
-  def validate_each(record, attr_name, value, ...)
-    super(record, attr_name, value, ...)
-
-    if options[:precision] || options[:scale]
-      attr_type = record.class.type_for_attribute(attr_name)
-      # For conversion of 'value' to BigDecimal 'ndigits' is not supplied intentionally,
-      # to avoid silent rounding. It is only required for conversion from Float and
-      # Rational, which should not happen.
-      value = BigDecimal(value) unless value.is_a? BigDecimal
-      if options[:precision] && (value.precision > attr_type.precision)
-        record.errors.add(attr_name, :precision_exceeded, **filtered_options(attr_type.precision))
-      end
-      if options[:scale] && (value.scale > attr_type.scale)
-        record.errors.add(attr_name, :scale_exceeded, **filtered_options(attr_type.scale))
-      end
-    end
-  end
-end

lib/core_ext/big_decimal_scientific_notation.rb

@@ -1,36 +0,0 @@
-module CoreExt
-  module BigDecimalScientificNotation
-    def to_scientific
-      return 'NaN' unless finite?
-
-      sign, coefficient, base, exponent = split
-      (sign == -1 ? '-' : '') +
-        (coefficient.length > 1 ? coefficient.insert(1, '.') : coefficient) +
-        (exponent != 1 ? "e#{exponent-1}" : '')
-    end
-
-    # Converts value to HTML formatted scientific notation
-    def to_html
-      sign, coefficient, base, exponent = split
-      return 'NaN' unless sign
-
-      result = (sign == -1 ? '-' : '')
-      unless coefficient == '1' && sign == 1
-        if coefficient.length > 1
-          result += coefficient.insert(1, '.')
-        elsif
-          result += coefficient
-        end
-        if exponent != 1
-          result += "×"
-        end
-      end
-      if exponent != 1
-        result += "10<sup>% d</sup>" % [exponent-1]
-      end
-      result.html_safe
-    end
-  end
-end
-
-BigDecimal.prepend CoreExt::BigDecimalScientificNotation

lib/core_ext/float.rb

@@ -0,0 +1,54 @@
+# If a decimal string with at most 15 significant digits is converted to the
+# IEEE 754 double-precision format, giving a normal number, and then converted
+# back to a decimal string with the same number of digits, the final result
+# should match the original string.
+# If an IEEE 754 double-precision number is converted to a decimal string with
+# at least 17 significant digits, and then converted back to double-precision
+# representation, the final result must match the original number:
+#   ("%.16e" % self).to_f == self
+class Float
+  def to_scientific
+    sign, significand, exponent = split
+    sign + significand + (exponent != 0 ? "e#{exponent}" : '')
+  end
+
+  # Converts value to HTML formatted scientific notation.
+  def to_html(show_unity: true)
+    result, significand, exponent = split
+    result += significand if significand != '1' || (exponent == 0 && show_unity)
+    if exponent != 0
+      result += "×" if significand != '1'
+      result += "10<sup>% d</sup>" % exponent
+    end
+    result.html_safe
+  end
+
+  # Assume #finite? is true.
+  def limit(precision = DIG)
+    return 0.0 if precision.zero?
+    sign, significand, exponent = split(DIG_MAX)
+    "#{sign}#{significand[..precision]}e#{exponent}".to_f
+  end
+
+  private
+
+  SPLIT_FLOAT = /(-?)(.*?)\.?0*e(.*)/
+
+  # Format `%e` displays starting from significant digit (not 0).
+  def split(digits = DIG)
+    return ['', to_s[..2], 0] unless finite?
+    return ['', '0', 0] if digits.zero?
+    ("%.#{digits - 1}e" % self).match(SPLIT_FLOAT).captures
+      .then { |sign, significand, exponent| [sign, significand, exponent.to_i] }
+  end
+
+  # The maximum number of significant decimal digits in a double-precision
+  # floating point number.
+  DIG_MAX = 17
+  # Smallest and largest double-precision floating point numbers with DIG
+  # precision.
+  # TODO: change MIN_15 to MIN.ceil(MIN_10_EXP - DIG) after #ceil fix in Ruby
+  # v4.0.5: https://bugs.ruby-lang.org/issues/22079
+  MIN_15 = MIN.ceil(-(MIN_10_EXP - 1))
+  MAX_15 = MAX.floor(-(MAX_10_EXP - DIG + 1))
+end

lib/core_ext/range.rb

@@ -0,0 +1,31 @@
+class Range
+  # TODO: cleanup comments after commit
+  # * < nil, true < false
+  #if a.end == b.end
+  #  a.exclude_end? ^ b.exclude_end? ? (a.exclude_end? ? -1 : 1) : 0
+  #else
+  #  a.end <=> b.end || (a.end.nil? ? 1 : -1)
+  #end
+  #a.end == b.end ? (b.exclude_end? ? b : a) : [a, b].to_h.except(nil).min
+  #*(l[0] == r[0] ? (r[1] ? r : l) : [l, r].reject{ |e| e[0].nil? }.min)
+  def &(other)
+    case other
+    when Range
+      return nil unless self.overlap?(other)
+
+      both = [self, other]
+      return Range.new(
+        both.map(&:begin).compact.max,
+        *if self.end == other.end
+           other.exclude_end? ? [other] : [self]
+        else
+          both.select(&:end)
+        end.map { |r| [r.end, r.exclude_end?] }.min
+      )
+    when Array
+      return other.map { |o| self & o }.compact
+    else
+      return self.member?(other) ? other : nil
+    end
+  end
+end

lib/default_settings_strategy.rb

@@ -0,0 +1,55 @@
+class DefaultSettingsStrategy < ActiveRecord::Migration::DefaultStrategy
+  COLUMN_DEFAULTS = {
+    # TODO: all types `null: false` ?
+    # TODO: references `foreign_key: {on_delete: :cascade}` ?
+    # `timestamps` - Rails defaults to `null: false, precision: true`.
+    # `limit:` for `text` - `text` can be theoretically up to 1GB or
+    #   longer, so roughly unlimited for practical purposes. But:
+    #   * the actual usable length depends on additional factors, like compile
+    #     time limits (`SQLITE_MAX_LENGTH` in SQLite), runtime settings
+    #     (`max_allowed_packet` in MySQL) and probably other,
+    #   * Rails does not report limit for `text` column types, unless it is
+    #     explicitly set.
+    #   The decision is to always set safe limit and enforce it by validations, to
+    #   avoid surprises (e.g. text truncation) when saving to dabatase.
+    text: {limit: 2**16 - 1}
+  }
+  COLUMN_DEFAULTS.default = {}
+  COLUMN_DEFAULTS.freeze
+
+  module ColumnSettingsStrategy
+    def column(name, type, **options)
+      super(name, type, **COLUMN_DEFAULTS[type].merge(options))
+    end
+  end
+  ActiveRecord::ConnectionAdapters::TableDefinition.prepend ColumnSettingsStrategy
+
+  # `force: :cascade` - does nothing on MySQL, so `force:` is useless.
+  # `if_not_exists: true`/`if_exists: true` - without these options it's impossible
+  #   to change migration status once migration fails partially. If `up` migration
+  #   creates some, but not all objects, its status is not updated from `down` to
+  #   `up`. Then it's impossible to migrate: a) up - due to `already exists`
+  #   errors and b) down - due to migration status.
+  MIGRATION_DEFAULTS = {
+    add_check_constraint: {if_not_exists: true},
+    add_column:           {if_not_exists: true},
+    add_foreign_key:      {if_not_exists: true},
+    add_index:            {if_not_exists: true, unique: true},
+    add_timestamps:       {if_not_exists: true},
+    create_table:         {if_not_exists: true},
+    drop_table:               {if_exists: true},
+    remove_check_constraint:  {if_exists: true},
+    remove_column:            {if_exists: true},
+    remove_foreign_key:       {if_exists: true},
+    remove_index:             {if_exists: true},
+    remove_timestamps:        {if_exists: true},
+  }
+  MIGRATION_DEFAULTS.default = {}
+  MIGRATION_DEFAULTS.freeze
+
+  def method_missing(method, *args, **kwargs, &)
+    conflicts = kwargs.has_key?(:force) ? [:if_not_exists, :if_exists] : []
+    defaults = MIGRATION_DEFAULTS[method.to_sym].except(*conflicts)
+    super(method, *args, **defaults.merge(kwargs), &)
+  end
+end

public/icon.svg

@@ -0,0 +1,3 @@
+<svg width="512" height="512" xmlns="http://www.w3.org/2000/svg">
+  <circle cx="256" cy="256" r="256" fill="red"/>
+</svg>

test/application_system_test_case.rb

@@ -17,17 +17,20 @@ class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
     options.add_preference('browser.download.dir', "#{Rails.root}/tmp/")
   end
 
-  def sign_in(user: users.select(&:confirmed?).sample, password: randomize_user_password!(user))
+  def sign_in(user: users.select(&:confirmed?).sample,
+              password: randomize_user_password!(user))
     visit new_user_session_url
     fill_in User.human_attribute_name(:email), with: user.email
     fill_in User.human_attribute_name(:password), with: password
     click_on t(:sign_in)
+    yield if block_given?
     user
   end
 
-  def inject_button_to(after, *button_options)
+  def inject_button_to(inside, *button_options)
     button = button_to *button_options
-    evaluate_script("arguments[0].insertAdjacentHTML('beforeend', '#{button.html_safe}');", after)
+    inside.evaluate_script("this.insertAdjacentHTML('beforeend', arguments[0]);",
+                           button.html_safe)
   end
 
   # Allow skipping interpolations when translating for testing purposes
@@ -38,6 +41,32 @@ class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
   end
   alias :t :translate
 
+  DB_CONFIGS = ActiveRecord::Base.configurations.configs_for(env_name: "test")
+  TEST_CONFIGS = Hash.new(DB_CONFIGS.first.name.to_sym)
+  class << self
+    # NOTE: alternative to current solution is to create shards:
+    #   ActiveRecord::Base.connects_to(
+    #     shards: {mysql2: {writing: :mysql2}, sqlite3: {writing: :sqlite3}}
+    #   )
+    # and use them in one of the following ways:
+    # * set config.active_record.shard_selector/shard_resolver
+    # * run tests within: ActiveRecord::Base.connected_to(shard: :sqlite3) { test_ }
+    # Remove this note once current solution is confirmed to work.
+    #
+    # Test block should not be modified here, as it would change its binding from
+    # instance level to class level.
+    if DB_CONFIGS.many?
+      def test(name, ...)
+        DB_CONFIGS.each do |config|
+          TEST_CONFIGS[super("#{config.name} #{name}", ...)] = config.name.to_sym
+        end
+      end
+    end
+  end
+  setup do
+    ActiveRecord::Base.establish_connection(TEST_CONFIGS[name.to_sym])
+  end
+
   #def assert_stale(element)
   #  assert_raises(Selenium::WebDriver::Error::StaleElementReferenceError) { element.tag_name }
   #end

test/controllers/measurements_controller_test.rb

@@ -1,8 +0,0 @@
-require "test_helper"
-
-class MeasurementsControllerTest < ActionDispatch::IntegrationTest
-  #test "should get index" do
-  #  get measurements_index_url
-  #  assert_response :success
-  #end
-end

test/controllers/quantities_controller_test.rb

@@ -1,7 +0,0 @@
-require "test_helper"
-
-class QuantitiesControllerTest < ActionDispatch::IntegrationTest
-  # test "the truth" do
-  #   assert true
-  # end
-end

test/controllers/units_controller_test.rb

@@ -1,7 +0,0 @@
-require "test_helper"
-
-class UnitsControllerTest < ActionDispatch::IntegrationTest
-  # test "the truth" do
-  #   assert true
-  # end
-end

test/controllers/users_controller_test.rb

@@ -1,5 +1,7 @@
 require "test_helper"
 
+# TODO: make sure tested actions are covered by system tests and remove all
+# controller tests.
 class UsersControllerTest < ActionDispatch::IntegrationTest
   setup do
     @user = users(:one)

test/models/user_test.rb

@@ -1,7 +0,0 @@
-require "test_helper"
-
-class UserTest < ActiveSupport::TestCase
-  # test "the truth" do
-  #   assert true
-  # end
-end

test/system/quantities_test.rb

@@ -1,45 +0,0 @@
-require "application_system_test_case"
-
-class QuantitiesTest < ApplicationSystemTestCase
-  setup do
-    @user = sign_in(user: users(:alice))
-    @unit = @user.units.create!(symbol: 'kg')
-    @quantity = @user.quantities.create!(name: 'Weight')
-    visit quantities_path
-  end
-
-  test "update button turns red when default unit changes" do
-    click_on 'Weight'
-
-    button = find('button[name=button]')
-    initial_color = evaluate_script("getComputedStyle(arguments[0]).backgroundColor", button)
-
-    select 'kg', from: 'quantity[default_unit_id]'
-
-    changed_color = evaluate_script("getComputedStyle(arguments[0]).backgroundColor", button)
-    refute_equal initial_color, changed_color, "Button color should change when default unit is altered"
-  end
-
-  test "saving default unit pre-selects it in measurements form" do
-    click_on 'Weight'
-    select 'kg', from: 'quantity[default_unit_id]'
-    click_on t('helpers.submit.update')
-    assert_selector '.flash.notice'
-
-    @quantity.reload
-    assert_equal @unit.id, @quantity.default_unit_id
-
-    visit measurements_path
-    find(:link_or_button, t('measurements.index.new_measurement')).click
-    assert_selector '#measurement_form'
-
-    within '#quantity_select' do
-      check 'Weight'
-    end
-    find('button[formaction]').click
-
-    within 'tbody#readouts' do
-      assert_selector "option[value='#{@unit.id}'][selected]"
-    end
-  end
-end

test/system/tasks_test.rb

@@ -0,0 +1,20 @@
+require 'application_system_test_case'
+
+Rails.application.load_tasks
+# NOTE: for some reason task for checking pending migrations messes up
+# transaction when run during test. It causes all DB changes made before its
+# execution to be rolled back.
+# Run it before tests, so any rake task dependent on it will see it as
+# #already_invoked and won't run it during test. It is redundant anyway, as
+# migrations are run before starting test suite.
+Rake::Task['db:abort_if_pending_migrations'].invoke
+
+class TasksTest < ApplicationSystemTestCase
+  test "db:seed creates admin account" do
+    User.admin.delete_all
+    assert_output /Creating admin account/ do
+      Rake::Task['db:seed'].execute
+    end
+    assert User.admin.exists?
+  end
+end

test/system/units_test.rb

@@ -1,33 +1,36 @@
 require "application_system_test_case"
 
 # Fixture prerequisites:
-#  * user with multiple units + subunits
-#  * user with single unit
-#  * user with no units
+#  * user with multiple units (at least 1 w/o subunit) + subunits,
+#  * user with single unit,
+# FIXME: add confirmed user without units
+#  * user with no units.
+# Users need to be active and confirmed.
 
 class UnitsTest < ApplicationSystemTestCase
-  LINK_LABELS = {}
+  def sign_in(...)
+    @link_labels = nil
+    @user = super { click_on t('units.navigation') }
+  end
 
-  setup do
-    @user = sign_in
-
-    LINK_LABELS.clear
-    LINK_LABELS[:new_unit] = t('units.index.new_unit')
-    LINK_LABELS[:new_subunit] = t('units.unit.new_subunit')
-    LINK_LABELS[:edit] = Regexp.union(@user.units.map(&:symbol))
-
-    visit units_path
+  def link_labels
+    @link_labels ||= {
+      new_unit:     t('units.index.new_unit'),
+      new_subunit:  t('units.unit.new_subunit'),
+      edit:         Regexp.union(@user.units.map(&:symbol))
+    }
   end
 
   test "index" do
-    # Wait for the table to appear first, only then check row count
+    sign_in
+    # Wait for the table to appear first, only then check row count.
     within 'tbody' do
       assert_selector 'tr', count: @user.units.count
     end
 
-    # Cannot #destroy_all due to {dependent: :restrict*} on Unit.subunits association
+    # Cannot #destroy_all due to {dependent: :restrict*} on Unit.subunits association.
     @user.units.delete_all
-    visit units_path
+    refresh
     within 'tbody' do
       assert_selector 'tr', count: 1
       assert_text t('units.no_items')
@@ -35,7 +38,9 @@ class UnitsTest < ApplicationSystemTestCase
   end
 
   test "new and create" do
-    type, label = LINK_LABELS.assoc([:new_unit, :new_subunit].sample)
+    sign_in
+    link_labels.slice!(:new_unit, :new_subunit)
+    type, label = link_labels.to_a.sample
     new_link = all(:link, exact_text: label).sample
     new_link.click
     assert_equal 'disabled', new_link[:disabled]
@@ -44,10 +49,12 @@ class UnitsTest < ApplicationSystemTestCase
     within 'tbody > tr:has(input[type=text], textarea)' do
       assert_selector ':focus'
 
-      maxlength = all(:fillable_field).to_h { |f| [f[:name], f[:maxlength].to_i || 2**16] }
+      maxlength = all(:fillable_field).to_h do |field|
+        [field[:name], field[:maxlength].to_i || 2**16]
+      end
       values = {
-        symbol: random_string(rand([1..3, 4..maxlength['unit[symbol]']].sample),
-                              except: units.map(&:symbol)),
+        symbol: random_string(deep_rand(1..3, 4..maxlength['unit[symbol]']),
+                              except: @user.units.map(&:symbol), allow_blank: false),
         description: random_string(rand(0..maxlength['unit[description]']))
       }.with_indifferent_access
       within :field, 'unit[multiplier]' do |field|
@@ -61,34 +68,60 @@ class UnitsTest < ApplicationSystemTestCase
       end
     end
 
-    assert_selector '.flash.notice', text: t('units.create.success', unit: Unit.last.symbol)
+    assert_selector '.flash.notice',
+      text: t('units.create.success', unit: Unit.last.symbol)
     within 'tbody' do
       assert_no_selector :fillable_field
       assert_selector 'tr', count: @user.units.count
     end
     assert_no_selector :element, :a, 'disabled': 'disabled',
-      exact_text: Regexp.union(LINK_LABELS.fetch_values(:new_unit, :new_subunit))
+      exact_text: Regexp.union(link_labels.values)
     assert_equal values, Unit.last.attributes.slice(*values.keys)
   end
 
+  test "create updates view in order" do
+    # Destroy and re-create unit to verify its index position is unchanged.
+    sign_in(user: users.select { |u| u.confirmed? && u.units.many? }.sample)
+
+    link = all(:link_or_button, exact_text: t('units.unit.destroy')).sample
+    symbol = link.ancestor('tr').first(:link).text
+    index = link.ancestor('tbody').all('tr').index { |e| e.first(:link).text == symbol }
+    unit = @user.units.find_by(symbol: symbol)
+
+    link.click
+    if unit.base_id?
+      find_link(unit.base.symbol).ancestor('tr').click_on(t('units.unit.new_subunit'))
+      fill_in 'unit[multiplier]', with: unit.multiplier
+    else
+      click_on t('units.index.new_unit')
+    end
+    fill_in 'unit[symbol]', with: unit.symbol
+    click_on t('helpers.submit.create')
+
+    within "tbody > tr:nth-child(#{index+1})" do
+      assert_selector :link, exact_text: symbol
+    end
+  end
+
   test "new and edit on validation error" do
-    # It's not possible to cause validation error on :edit with single unit
-    LINK_LABELS.delete(:edit) unless @user.units.count > 1
-    type, label = LINK_LABELS.to_a.sample
+    sign_in
+    # It's impossible to cause validation error on :edit with single unit.
+    link_labels.delete(:edit) unless @user.units.many?
+    type, label = link_labels.to_a.sample
     link = all(:link, exact_text: label).sample
     link.click
 
     get_values = -> { all(:field).map { |f| [f[:name], f[:value]] }.to_h }
     values = nil
     within 'tbody > tr:has(input[type=text])' do
-      # Provide duplicate :symbol as input invalidatable server side
+      # Provide duplicate :symbol as input invalidatable server side.
       fill_in 'unit[symbol]',
         with: (@user.units.map(&:symbol) - [find_field('unit[symbol]').value]).sample
       values = get_values[]
       send_keys :enter
     end
 
-    # Wait for flash before checking link :disabled status
+    # Wait for flash before checking link :disabled status.
     assert_selector '.flash.alert'
     if type == :edit
       assert_no_selector :link, exact_text: link[:text]
@@ -102,15 +135,18 @@ class UnitsTest < ApplicationSystemTestCase
   end
 
   test "new and edit allow opening multiple forms" do
-    # Requires at least 1 unit to be able to open 2 forms
-    links = LINK_LABELS.transform_values { |labels| all(:link, exact_text: labels).to_a }
+    # Require at least 1 unit to be able to open 2 forms.
+    sign_in(user: users.select { |u| u.confirmed? && u.units.any? }.sample)
+    links = link_labels.transform_values do |labels|
+      all(:link, exact_text: labels).to_a
+    end
     random_link = ->{ links.transform_values(&:sample).compact.to_a.sample }
-    # Define tr count change depending on link clicked
+    # Define <tr> count change depending on link clicked.
     tr_diff = {new_unit: 1, new_subunit: 1, edit: 0}
 
     type, link = random_link[].tap { |t, l| links[t].delete(l) }
     subunit_link = link.ancestor('tr')
-      .first(:link, LINK_LABELS[:new_subunit], between: 0..1) if type == :edit
+      .first(:link, link_labels[:new_subunit], between: 0..1) if type == :edit
     assert_difference ->{ all('tbody tr').count }, tr_diff[type] do
       assert_difference ->{ all('tbody tr:has(input[type=text])').count }, 1 do
         link.click
@@ -135,12 +171,14 @@ class UnitsTest < ApplicationSystemTestCase
     assert_not_equal form, find('tbody tr:has(input:focus)')
   end
 
-  #test "edit" do
+  test "edit" do
     # NOTE: Check if displayed attributes match record
-  #end
+    assert true
+  end
 
   # NOTE: extend with any add/edit link
-  test "close new unit form with escape key" do
+  test "new form closes on escape key" do
+    sign_in
     click_on t('units.index.new_unit')
     first('tbody > tr').all(:field).sample.send_keys :escape
     within 'tbody' do
@@ -149,7 +187,8 @@ class UnitsTest < ApplicationSystemTestCase
   end
 
   # NOTE: extend with any add/edit link
-  test "close and reopen new unit form" do
+  test "new form can be reopened after close" do
+    sign_in
     click_on t('units.index.new_unit')
     within 'tbody' do
       find(:link_or_button, exact_text: t(:cancel)).click
@@ -159,13 +198,19 @@ class UnitsTest < ApplicationSystemTestCase
     assert_selector 'tbody > tr:has(input, textarea)'
   end
 
+  test "rebase" do
+    # TODO
+    assert true
+  end
+
   test "destroy" do
+    sign_in(user: users.select { |u| u.confirmed? && u.units.any? }.sample)
     link = all(:link_or_button, exact_text: t('units.unit.destroy')).sample
-    label = link.ancestor('tr').first(:link)[:text]
+    symbol = link.ancestor('tr').first(:link).text
     assert_difference ->{ @user.units.count }, -1 do
       link.click
     end
     assert_selector 'tbody tr', count: [@user.units.count, 1].max
-    assert_selector '.flash.notice', text: t('units.destroy.success', unit: label)
+    assert_selector '.flash.notice', text: t('units.destroy.success', unit: symbol)
   end
 end

test/system/users_test.rb

@@ -1,5 +1,6 @@
 require "application_system_test_case"
 
+# TODO: review #visit usage and replace with #click_on where applicable
 class UsersTest < ApplicationSystemTestCase
   setup do
     @admin = users(:admin)
@@ -204,6 +205,7 @@ class UsersTest < ApplicationSystemTestCase
 
   test 'update profile' do
     # TODO
+    assert true
   end
 
   test 'update status' do
@@ -227,9 +229,10 @@ class UsersTest < ApplicationSystemTestCase
 
     within all(:xpath, "//tbody//tr[not(descendant::select)]").sample do |tr|
       user = User.find_by_email!(first(:link).text)
-      inject_button_to first('td:not(.link)'), "update status", user_path(user), method: :patch,
+      inject_button_to find('td', exact_text: user.status), "update status",
+        user_path(user), method: :patch,
         params: {user: {status: User.statuses.keys.sample}}, data: {turbo: false}
-      execute_script("arguments[0].click()", find_button("update status"))
+      click_on "update status"
     end
     assert_title 'The change you wanted was rejected (422)'
   end
@@ -237,8 +240,8 @@ class UsersTest < ApplicationSystemTestCase
   test 'update status forbidden for non admin' do
     sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     visit units_path
-    inject_button_to find('body'), "update status", user_path(User.all.sample), method: :patch,
-      params: {user: {status: User.statuses.keys.sample}}
+    inject_button_to find('body'), "update status", user_path(User.all.sample),
+      method: :patch, params: {user: {status: User.statuses.keys.sample}}
     click_on "update status"
     assert_text t('actioncontroller.exceptions.status.forbidden')
   end

test/test_helper.rb

@@ -3,9 +3,6 @@ require_relative "../config/environment"
 require "rails/test_help"
 
 class ActiveSupport::TestCase
-  # Run tests in parallel with specified workers
-  parallelize(workers: :number_of_processors)
-
   # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
   fixtures :all
 
@@ -13,27 +10,100 @@ class ActiveSupport::TestCase
   include ActionView::Helpers::TranslationHelper
 
   # List of categorized Unicode characters:
-  # * http://www.unicode.org/Public/UNIDATA/UnicodeData.txt
-  # File format: http://www.unicode.org/L2/L1999/UnicodeData.html
-  # Select from graphic ranges: L, M, N, P, S, Zs
-  UNICODE_CHARS = {
-    1 => [*"\u0020".."\u007E"],
-    2 => [*"\u00A0".."\u00AC",
-          *"\u00AE".."\u05FF",
-          *"\u0606".."\u061B",
-          *"\u061D".."\u06DC",
-          *"\u06DE".."\u070E",
-          *"\u0710".."\u07FF"]
-  }
-  UNICODE_CHARS.default = UNICODE_CHARS[1] + UNICODE_CHARS[2]
-  def random_string(bytes = 10, except: [])
+  #   * source: http://www.unicode.org/Public/UNIDATA/UnicodeData.txt
+  #   * file format: http://www.unicode.org/L2/L1999/UnicodeData.html
+  #   * select from graphic ranges: L, M, N, P, S, Zs
+  UNICODE_CHARS = [
+    *"\u0020".."\u007E",
+    *"\u00A0".."\u00AC",
+    *"\u00AE".."\u05FF",
+    *"\u0606".."\u061B",
+    *"\u061D".."\u06DC",
+    *"\u06DE".."\u070E",
+    *"\u0710".."\u07FF"
+  ]
+  def random_string(length, except: [], allow_blank: true)
+    # Rails String#blank? is based on [[:space:]] character class (String::BLANK_RE).
+    # Here we use more general class including tabs, cariage returns and newlines.
+    except << /^\p{Space}+$/ unless allow_blank
     begin
-      result = ''
-      result += UNICODE_CHARS[bytes - result.bytesize].sample while bytes > result.bytesize
-    end while except.include?(result)
+      result = UNICODE_CHARS.sample(length).join
+    end while except.any? { |e| e === result }
     result
   end
 
+  # Range based string generation. Not finished, but saved as a potential
+  # reference for future work. To work properly it needs to sort in collation
+  # order of database.
+  #def random_between(from, to, maxlength)
+  #  # TODO: sort UNICODE_CHARS
+  #  byebug
+  #  result = ''
+  #  maxlength.times do |i|
+  #    case
+  #    when from[i] == to[i]
+  #      result += from[i]
+  #    else
+  #      from_index = UNICODE_CHARS.bsearch_index(from[i] || UNICODE_CHARS[0])
+  #      to_index = UNICODE_CHARS.bsearch_index(to[i])
+  #      index = rand(from_index..to_index)
+  #      case
+  #      when index == from_index
+  #        result += UNICODE_CHARS[index]
+  #        from[i+1..].each_char do |c|
+  #          from_index = UNICODE_CHARS.bsearch_index(from[i])
+  #          index = rand(from_index..UNICODE_CHARS.length-1)
+  #          result += UNICODE_CHARS[index]
+  #          break if index != from_index
+  #        end
+  #        if result == from
+  #          if result.length < maxlength
+  #            result += UNICODE_CHARS.sample
+  #          else
+  #            # TODO: succ result[i..]
+  #            # raise if result == to
+  #          end
+  #        end
+  #        break
+  #      when index == to_index
+  #        result += UNICODE_CHARS[index]
+  #        to[i+1..].each_char do |c|
+  #          to_index = UNICODE_CHARS.bsearch_index(to[i])
+  #          index = rand(-1..to_index)
+  #          break if index == -1
+  #          result += UNICODE_CHARS[index]
+  #          break if index != to_index
+  #        end
+  #        if result == to
+  #          if result.length > i+1
+  #            result = result[..-2]
+  #          else
+  #            # TODO: prev result[i..]
+  #            # raise if result == from
+  #          end
+  #        end
+  #        break
+  #      else
+  #        result += UNICODE_CHARS[index]
+  #        break
+  #      end
+  #    end
+  #  end
+  #  return result += UNICODE_CHARS.sample(rand(0..maxlength-i-1)).join
+  #  # if result == from/to ...
+  #end
+
+  def deep_rand(*args)
+    case args
+    when Array
+      args = args.sample
+    when Range
+      args = rand(args)
+    else
+      return args
+    end while true
+  end
+
   # Assumes: max >= step and step = 1e[-]N, both as strings
   def random_number(max, step)
     max.delete!('.')