reset `ActionMailer::Base.deliveries` in `ActionDispatch::IntegrationTest`.

Whenever you are sending emails in integration tests using the `:test`
delivery method you need to make sure that
`ActionMailer::Base.deliveries` is reset after every test. This piece of
boilerplate code is present in all my applications that send
emails. Let's have `ActionDispatch::IntegrationTest` reset the
deliveries automatically.

1 files changed, 46 insertions, 0 deletions

diff --git a/railties/test/application/integration_test_case_test.rb b/railties/test/application/integration_test_case_test.rb
new file mode 100644
index 0000000000..40a79fc636
--- /dev/null
+++ b/railties/test/application/integration_test_case_test.rb
@@ -0,0 +1,46 @@
+require 'isolation/abstract_unit'
+
+module ApplicationTests
+  class IntegrationTestCaseTest < ActiveSupport::TestCase
+    include ActiveSupport::Testing::Isolation
+
+    setup do
+      build_app
+      boot_rails
+    end
+
+    teardown do
+      teardown_app
+    end
+
+    test "resets Action Mailer test deliveries" do
+      script('generate mailer BaseMailer welcome')
+
+      app_file 'test/integration/mailer_integration_test.rb', <<-RUBY
+        require 'test_helper'
+
+        class MailerIntegrationTest < ActionDispatch::IntegrationTest
+          setup do
+            @old_delivery_method = ActionMailer::Base.delivery_method
+            ActionMailer::Base.delivery_method = :test
+          end
+
+          teardown do
+            ActionMailer::Base.delivery_method = @old_delivery_method
+          end
+
+          2.times do |i|
+            define_method "test_resets_deliveries_\#{i}" do
+              BaseMailer.welcome.deliver_now
+              assert_equal 1, ActionMailer::Base.deliveries.count
+            end
+          end
+        end
+      RUBY
+
+      output = Dir.chdir(app_path) { `bin/rails test 2>&1` }
+      assert_equal 0, $?.to_i, output
+      assert_match /0 failures, 0 errors/, output
+    end
+  end
+end