diff --git a/config/database.yml.dist b/config/database.yml.dist
index b704041..206381a 100644
--- a/config/database.yml.dist
+++ b/config/database.yml.dist
@@ -26,6 +26,7 @@
 default: &default
   adapter: mysql2
   encoding: utf8mb4
+  collation: utf8mb4_0900_as_ci
   pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
   username: fixinme
   password:
diff --git a/test/system/units_test.rb b/test/system/units_test.rb
index cbdd625..55c0b7b 100644
--- a/test/system/units_test.rb
+++ b/test/system/units_test.rb
@@ -29,23 +29,27 @@ class UnitsTest < ApplicationSystemTestCase
     end
   end
 
-  test "new" do
+  test "new and create" do
     type, label = LINK_LABELS.assoc([:add_unit, :add_subunit].sample)
     add_link = all(:link, exact_text: label).sample
     add_link.click
     assert_equal 'disabled', add_link[:disabled]
 
+    params = nil
     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] }
-
-      fill_in 'unit[symbol]',
-        with: random_string(rand([1..3, 4..maxlength['unit[symbol]']].sample))
-      fill_in 'unit[description]', with: random_string(rand(0..maxlength['unit[description]']))
+      params = {
+        symbol: random_string(rand([1..3, 4..maxlength['unit[symbol]']].sample),
+                              except: units.map(&:symbol)),
+        description: random_string(rand(0..maxlength['unit[description]']))
+      }.with_indifferent_access
       within :field, 'unit[multiplier]' do |field|
-        fill_in with: random_number(field[:max], field[:step])
-      end if add_link[:text] != t('units.index.add_unit')
+        params[:multiplier] = random_number(field[:max], field[:step])
+      end if type == :add_subunit
+
+      params.each_pair { |name, value| fill_in "unit[#{name}]", with: value }
 
       assert_difference ->{ Unit.count }, 1 do
         click_on t('helpers.submit.create')
@@ -58,7 +62,8 @@ class UnitsTest < ApplicationSystemTestCase
     end
     assert_no_selector :element, :a, 'disabled': 'disabled',
       exact_text: Regexp.union(LINK_LABELS.fetch_values(:add_unit, :add_subunit))
-    assert_selector '.flash.notice', text: t('units.create.success', unit: Unit.all.last.symbol)
+    assert_selector '.flash.notice', text: t('units.create.success', unit: Unit.last.symbol)
+    assert_equal params, Unit.last.attributes.slice(*params.keys)
   end
 
   # TODO: check proper form/button redisplay and flash messages on add/edit
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 183e6e8..5362a8d 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -26,11 +26,11 @@ class ActiveSupport::TestCase
           *"\u0710".."\u07FF"]
   }
   UNICODE_CHARS.default = UNICODE_CHARS[1] + UNICODE_CHARS[2]
-  def random_string(bytes = 10)
-    result = ''
-    while bytes > 0
-      result += UNICODE_CHARS[bytes].sample.tap { |c| bytes -= c.bytesize }
-    end
+  def random_string(bytes = 10, except: [])
+    begin
+      result = ''
+      result += UNICODE_CHARS[bytes - result.bytesize].sample while bytes > result.bytesize
+    end while except.include?(result)
     result
   end