fixture file will validate fixture format

activerecord/lib/active_record/fixtures/file.rb

@@ -34,12 +34,19 @@ module ActiveRecord
         return @rows if @rows
 
         data = YAML.load(render(IO.read(@file)))
-        @rows = data ? data.to_a : []
+        @rows = data ? validate(data).to_a : []
       end
 
       def render(content)
         ERB.new(content).result
       end
+
+      # Validate our unmarshalled data.
+      def validate(data)
+        raise Fixture::FormatError, 'fixture is not a hash' unless Hash === data
+        raise Fixture::FormatError unless data.all? { |name, row| Hash === row }
+        data
+      end
     end
   end
 end

activerecord/test/cases/fixtures/file_test.rb

@@ -48,6 +48,24 @@ module ActiveRecord
         end
       end
 
+      # A valid YAML file is not necessarily a value Fixture file. Make sure
+      # an exception is raised if the format is not valid Fixture format.
+      def test_wrong_fixture_format_string
+        tmp_yaml ['empty', 'yml'], 'qwerty' do |t|
+          assert_raises(ActiveRecord::Fixture::FormatError) do
+            File.open(t.path) { |fh| fh.to_a }
+          end
+        end
+      end
+
+      def test_wrong_fixture_format_nested
+        tmp_yaml ['empty', 'yml'], 'one: two' do |t|
+          assert_raises(ActiveRecord::Fixture::FormatError) do
+            File.open(t.path) { |fh| fh.to_a }
+          end
+        end
+      end
+
       private
       def tmp_yaml(name, contents)
         t = Tempfile.new name