Add comprehensive unit test coverage for controllers, models, and services

- Translate French comments to English in controllers and tests
- Fix test failures: route helpers, validations, MySQL transaction issues
- Add Timecop for time-dependent tests and update database config for isolation

test/controllers/concerns/stripe_concern_test.rb

@@ -0,0 +1,33 @@
+require "test_helper"
+
+class StripeConcernTest < ActionDispatch::IntegrationTest
+  setup do
+    Rails.application.config.stripe = { secret_key: nil }
+  end
+
+  test "stripe_configured? returns false when no secret key" do
+    controller = ApplicationController.new
+    controller.extend StripeConcern
+    assert_not controller.stripe_configured?
+  end
+
+  test "stripe_configured? returns true when secret key present" do
+    Rails.application.config.stripe = { secret_key: "sk_test_key" }
+    controller = ApplicationController.new
+    controller.extend StripeConcern
+    assert controller.stripe_configured?
+  end
+
+  test "initialize_stripe returns false when not configured" do
+    controller = ApplicationController.new
+    controller.extend StripeConcern
+    assert_not controller.initialize_stripe
+  end
+
+  test "initialize_stripe returns true when configured" do
+    Rails.application.config.stripe = { secret_key: "sk_test_key" }
+    controller = ApplicationController.new
+    controller.extend StripeConcern
+    assert controller.initialize_stripe
+  end
+end