Update test/over_react/component_declaration/builder_integration_test…

…s/new_boilerplate/function_component_test.dart

Co-authored-by: Greg Littlefield <greg.littlefield@workiva.com>

test/over_react/component_declaration/builder_integration_tests/new_boilerplate/function_component_test.dart

@@ -411,7 +411,7 @@ testPropsToForward({UiFactory<TestProps> factory, bool modifyProps = false}) {
 
       test('which throws an error when not providing an exclude argument and the props class is NOT a mixin and `domOnly` is NOT `true`', () {
         expect(() => _propsToForward(exclude: null, props: initialProps, factory: factory, modifyProps: modifyProps),
-            throwsA(isA<AssertionError>()));
+            throwsA(isA<AssertionError>().having('toString value', (e) => e.toString(), contains('If this is not a props mixin, you need to specify its mixins as the second argument')));
       }, tags: 'ddc');
     });
 }