Fix column header lookup fragility, add fetch error handling, add tests

- Replace position-based column header lookup (ths[3]/ths[4]) with
  data-column attribute selectors — immune to column reordering
- Add .catch() error handlers to editMeasurementWide and setDefaultUnit
  fetch calls so failures surface in the console instead of silently
  disappearing
- Add MeasurementsController integration tests covering index auth,
  create with taken_at, empty-readout create, destroy, cross-user
  destroy isolation, and update

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/javascript/application.js

@@ -47,10 +47,8 @@ function buildWideTable() {
     groupMap.get(key).rows.push(r);
   });
 
-  // Read column headers from compact thead
-  var ths = document.querySelectorAll('.measurements-compact thead th');
-  var takenAtHeader = ths[3] ? ths[3].textContent : '';
-  var createdAtHeader = ths[4] ? ths[4].textContent : '';
+  var takenAtHeader = (document.querySelector('[data-column="taken-at"]') || {}).textContent || '';
+  var createdAtHeader = (document.querySelector('[data-column="created-at"]') || {}).textContent || '';
 
   var table = document.createElement('table');
   table.className = 'items-table';
@@ -190,7 +188,8 @@ function editMeasurementWide(url) {
         panel.scrollIntoView({behavior: 'smooth', block: 'nearest'});
       }
     });
-  });
+  })
+  .catch(err => console.error('editMeasurementWide failed:', err));
 }
 window.editMeasurementWide = editMeasurementWide
 
@@ -229,7 +228,8 @@ function setDefaultUnit(button) {
     }
     return response.text();
   })
-  .then(html => Turbo.renderStreamMessage(html));
+  .then(html => Turbo.renderStreamMessage(html))
+  .catch(err => console.error('setDefaultUnit failed:', err));
 }
 window.setDefaultUnit = setDefaultUnit
 

app/views/measurements/index.html.erb

@@ -21,8 +21,8 @@
         <th><%= Quantity.model_name.human %></th>
         <th><%= Readout.human_attribute_name(:value) %></th>
         <th><%= Unit.model_name.human %></th>
-        <th><%= Readout.human_attribute_name(:taken_at) %></th>
-        <th><%= Readout.human_attribute_name(:created_at) %></th>
+        <th data-column="taken-at"><%= Readout.human_attribute_name(:taken_at) %></th>
+        <th data-column="created-at"><%= Readout.human_attribute_name(:created_at) %></th>
         <% if current_user.at_least(:active) %>
           <th></th>
         <% end %>

test/controllers/measurements_controller_test.rb

@@ -1,7 +1,65 @@
 require "test_helper"
 
 class MeasurementsControllerTest < ActionDispatch::IntegrationTest
-  # test "the truth" do
-  #   assert true
-  # end
+  setup do
+    host! '127.0.0.1'
+    @user = users(:alice)
+    post new_user_session_path, params: { user: { email: @user.email, password: 'alice' } }
+    @quantity = @user.quantities.create!(name: 'Weight')
+    @unit = @user.units.create!(symbol: 'kg')
+  end
+
+  test "index returns ok" do
+    get measurements_path
+    assert_response :success
+  end
+
+  test "index requires authentication" do
+    delete destroy_user_session_path
+    get measurements_path
+    assert_response :redirect
+  end
+
+  test "create records readout with taken_at" do
+    taken_at = 1.day.ago.change(usec: 0)
+    assert_difference -> { @user.readouts.count } do
+      post measurements_path, params: {
+        taken_at: taken_at.iso8601,
+        readouts: [{ quantity_id: @quantity.id, value: '82.5', unit_id: @unit.id }]
+      }, as: :turbo_stream
+    end
+    assert_response :success
+    assert_equal taken_at, @user.readouts.last.taken_at
+  end
+
+  test "create with no readouts selected shows alert" do
+    post measurements_path, params: { taken_at: Time.now.iso8601 }, as: :turbo_stream
+    assert_response :success
+  end
+
+  test "destroy removes readout" do
+    readout = @user.readouts.create!(quantity: @quantity, unit: @unit, value: 82.5, taken_at: 1.day.ago)
+    assert_difference -> { @user.readouts.count }, -1 do
+      delete measurement_path(readout), as: :turbo_stream
+    end
+    assert_response :success
+  end
+
+  test "destroy cannot remove another user's readout" do
+    other_quantity = users(:bob).quantities.create!(name: 'Weight')
+    other_unit = users(:bob).units.create!(symbol: 'kg')
+    readout = users(:bob).readouts.create!(quantity: other_quantity, unit: other_unit, value: 70.0, taken_at: 1.day.ago)
+    assert_no_difference -> { users(:bob).readouts.count } do
+      delete measurement_path(readout), as: :turbo_stream
+    end
+  end
+
+  test "update changes readout value" do
+    readout = @user.readouts.create!(quantity: @quantity, unit: @unit, value: 82.5, taken_at: 1.day.ago)
+    patch measurement_path(readout), params: {
+      readout: { value: '83.0', unit_id: @unit.id, taken_at: readout.taken_at.iso8601 }
+    }, as: :turbo_stream
+    assert_response :success
+    assert_in_delta 83.0, readout.reload.value
+  end
 end