Require explicit adapter/serializer to render JSON API errors

- Separate collection errors from resource errors in adapter
- Refactor to ErrorsSerializer; first-class json error methods
- DOCS
- Rails 4.0 requires assert exact exception class, boo

test/adapter/json_api/errors_test.rb

@@ -23,7 +23,7 @@ module ActiveModelSerializers
           assert_equal serializable_resource.serializer_instance.object, @resource
 
           expected_errors_object =
-            { 'errors'.freeze =>
+            { :errors =>
               [
                 {
                   source: { pointer: '/data/attributes/name' },
@@ -49,7 +49,7 @@ module ActiveModelSerializers
           assert_equal serializable_resource.serializer_instance.object, @resource
 
           expected_errors_object =
-            { 'errors'.freeze =>
+            { :errors =>
               [
                 { :source => { :pointer => '/data/attributes/name' }, :detail => 'cannot be nil' },
                 { :source => { :pointer => '/data/attributes/name' }, :detail => 'must be longer' },
@@ -58,6 +58,20 @@ module ActiveModelSerializers
           }
           assert_equal serializable_resource.as_json, expected_errors_object
         end
+
+        # see http://jsonapi.org/examples/
+        def test_parameter_source_type_error
+          parameter = 'auther'
+          error_source = ActiveModelSerializers::Adapter::JsonApi::Error.error_source(:parameter, parameter)
+          assert_equal({ parameter: parameter }, error_source)
+        end
+
+        def test_unknown_source_type_error
+          value = 'auther'
+          assert_raises(ActiveModelSerializers::Adapter::JsonApi::Error::UnknownSourceTypeError) do
+            ActiveModelSerializers::Adapter::JsonApi::Error.error_source(:hyper, value)
+          end
+        end
       end
     end
   end