fix tests

Author: wasabeef

test/flutter_gen_test.dart

@@ -153,28 +153,33 @@ void main() {
       );
     });
 
-// test('Assets with No lists on pubspec.yaml', () async {
-//   expect(() async {
-//     return FlutterGenerator(
-//             File('test_resources/pubspec_assets_no_list.yaml'))
-//         .build();
-//   }, throwsA(isA<InvalidSettingsException>()));
-// });
-//
-// test('Wrong fonts settings on pubspec.yaml', () async {
-//   expect(() async {
-//     return FlutterGenerator(
-//             File('test_resources/pubspec_fonts_no_family.yaml'))
-//         .build();
-//   }, throwsA(isA<InvalidSettingsException>()));
-// });
-//
-// test('Wrong colors settings on pubspec.yaml', () async {
-//   expect(() async {
-//     return FlutterGenerator(
-//             File('test_resources/pubspec_colors_no_inputs.yaml'))
-//         .build();
-//   }, throwsA(isA<InvalidSettingsException>()));
-// });
+    test('Assets with No lists on pubspec.yaml', () async {
+      await FlutterGenerator(File('test_resources/pubspec_assets_no_list.yaml'))
+          .build();
+      expect(
+        File('test_resources/lib/gen/assets.gen.dart').existsSync(),
+        isFalse,
+      );
+    });
+
+    test('Wrong fonts settings on pubspec.yaml', () async {
+      await FlutterGenerator(
+              File('test_resources/pubspec_fonts_no_family.yaml'))
+          .build();
+      expect(
+        File('test_resources/lib/gen/fonts.gen.dart').existsSync(),
+        isFalse,
+      );
+    });
+
+    test('Wrong colors settings on pubspec.yaml', () async {
+      await FlutterGenerator(
+              File('test_resources/pubspec_colors_no_inputs.yaml'))
+          .build();
+      expect(
+        File('test_resources/lib/gen/colors.gen.dart').existsSync(),
+        isFalse,
+      );
+    });
   });
 }