Attempt to fix random CI failures

spec/support/database_cleaner.rb

@@ -1,21 +1,42 @@
 RSpec.configure do |config|
   config.before(:suite) do
+    if config.use_transactional_fixtures?
+      raise(<<-MSG)
+        Delete line `config.use_transactional_fixtures = true` from rails_helper.rb
+        (or set it to false) to prevent uncommitted transactions being used in
+        JavaScript-dependent specs.
+
+        During testing, the app-under-test that the browser driver connects to
+        uses a different database connection to the database connection used by
+        the spec. The app's database connection would not be able to access
+        uncommitted transaction data setup over the spec's database connection.
+      MSG
+    end
     DatabaseCleaner.clean_with(:truncation)
   end
 
   config.before(:each) do
     DatabaseCleaner.strategy = :transaction
   end
 
-  config.before(:each, :js => true) do
-    DatabaseCleaner.strategy = :truncation
+  config.before(:each, type: :feature) do
+    # :rack_test driver's Rack app under test shares database connection
+    # with the specs, so continue to use transaction strategy for speed.
+    driver_shares_db_connection_with_specs = Capybara.current_driver == :rack_test
+
+    unless driver_shares_db_connection_with_specs
+      # Driver is probably for an external browser with an app
+      # under test that does *not* share a database connection with the
+      # specs, so use truncation strategy.
+      DatabaseCleaner.strategy = :truncation
+    end
   end
 
   config.before(:each) do
     DatabaseCleaner.start
   end
 
-  config.after(:each) do
+  config.append_after(:each) do
     DatabaseCleaner.clean
   end
 end