Add database_cleaner to keep integration tests isolated.

If we create/modify/delete records (via requests) in integration tests,
it might affect other tests' test result. The ideal way is to keep
integration test data isolated. And by adding database_cleaner, we can
make sure database is reset between each test cases.

jsonapi-resources.gemspec

@@ -26,6 +26,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'pry'
   spec.add_development_dependency 'concurrent-ruby-ext'
+  spec.add_development_dependency 'database_cleaner'
   spec.add_dependency 'activerecord', '>= 4.1'
   spec.add_dependency 'railties', '>= 4.1'
   spec.add_dependency 'concurrent-ruby'

test/integration/requests/request_test.rb

@@ -2,12 +2,17 @@
 
 class RequestTest < ActionDispatch::IntegrationTest
   def setup
+    DatabaseCleaner.start
     JSONAPI.configuration.json_key_format = :underscored_key
     JSONAPI.configuration.route_format = :underscored_route
     Api::V2::BookResource.paginator :offset
     $test_user = Person.find(1001)
   end
 
+  def teardown
+    DatabaseCleaner.clean
+  end
+
   def after_teardown
     JSONAPI.configuration.route_format = :underscored_route
   end

test/test_helper.rb

@@ -1,4 +1,5 @@
 require 'simplecov'
+require 'database_cleaner'
 
 # To run tests with coverage:
 # COVERAGE=true bundle exec rake test
@@ -443,6 +444,8 @@ class CatResource < JSONAPI::Resource
   jsonapi_resources :people
 end
 
+DatabaseCleaner.strategy = :transaction
+
 # Ensure backward compatibility with Minitest 4
 Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)