Confirm caching attributes with different key json_api vs. attributes adapter

Adapted from @kevintyll's original test
#1644 (comment)

Author: bf4

test/cache_test.rb

@@ -171,6 +171,78 @@ def test_uses_adapter_in_cache_key
       assert_equal(@post_serializer.attributes, cache_store.fetch(key))
     end
 
+    # Based on original failing test by @kevintyll
+    # rubocop:disable Metrics/AbcSize
+    def test_a_serializer_rendered_by_two_adapter_returns_differently_cached_attributes
+      Object.const_set(:Alert, Class.new(ActiveModelSerializers::Model) do
+        attr_accessor :id, :status, :resource, :started_at, :ended_at, :updated_at, :created_at
+      end)
+      Object.const_set(:UncachedAlertSerializer, Class.new(ActiveModel::Serializer) do
+        attributes :id, :status, :resource, :started_at, :ended_at, :updated_at, :created_at
+      end)
+      Object.const_set(:AlertSerializer, Class.new(UncachedAlertSerializer) do
+        cache
+      end)
+
+      alert = Alert.new(
+        id: 1,
+        status: 'fail',
+        resource: 'resource-1',
+        started_at: Time.new(2016, 3, 31, 21, 36, 35, 0),
+        ended_at: nil,
+        updated_at: Time.new(2016, 3, 31, 21, 27, 35, 0),
+        created_at: Time.new(2016, 3, 31, 21, 37, 35, 0)
+      )
+
+      expected_cached_attributes = {
+        id: 1,
+        status: 'fail',
+        resource: 'resource-1',
+        started_at: alert.started_at,
+        ended_at: nil,
+        updated_at: alert.updated_at,
+        created_at: alert.created_at
+      }
+      expected_cached_jsonapi_attributes = {
+        id: '1',
+        type: 'alerts',
+        attributes: {
+          status: 'fail',
+          resource: 'resource-1',
+          started_at: alert.started_at,
+          ended_at: nil,
+          updated_at: alert.updated_at,
+          created_at: alert.created_at
+        }
+      }
+
+      # Assert attributes are serialized correctly
+      serializable_alert = serializable(alert, serializer: AlertSerializer, adapter: :attributes)
+      attributes_serialization = serializable_alert.as_json
+      assert_equal expected_cached_attributes, alert.attributes
+      assert_equal alert.attributes, attributes_serialization
+      attributes_cache_key = CachedSerializer.new(serializable_alert.adapter.serializer).cache_key(serializable_alert.adapter)
+      assert_equal attributes_serialization, cache_store.fetch(attributes_cache_key)
+
+      serializable_alert = serializable(alert, serializer: AlertSerializer, adapter: :json_api)
+      jsonapi_cache_key = CachedSerializer.new(serializable_alert.adapter.serializer).cache_key(serializable_alert.adapter)
+      # Assert cache keys differ
+      refute_equal attributes_cache_key, jsonapi_cache_key
+      # Assert (cached) serializations differ
+      jsonapi_serialization = serializable_alert.as_json
+      assert_equal alert.status, jsonapi_serialization.fetch(:data).fetch(:attributes).fetch(:status)
+      serializable_alert = serializable(alert, serializer: UncachedAlertSerializer, adapter: :json_api)
+      assert_equal serializable_alert.as_json, jsonapi_serialization
+
+      cached_serialization = cache_store.fetch(jsonapi_cache_key)
+      assert_equal expected_cached_jsonapi_attributes, cached_serialization
+    ensure
+      Object.send(:remove_const, :Alert)
+      Object.send(:remove_const, :AlertSerializer)
+      Object.send(:remove_const, :UncachedAlertSerializer)
+    end
+    # rubocop:enable Metrics/AbcSize
+
     def test_uses_file_digest_in_cache_key
       render_object_with_cache(@blog)
       key = "#{@blog.cache_key}/#{adapter.cached_name}/#{@blog.class.const_get(:FILE_DIGEST)}"