Test Runners

Test runners are the methods that are used to declare and define tests. Typically, golden tests are defined with the testWidgets() test runner. However, flutter_test_goldens comes with its own test runners for convenience, e.g., testGoldenScene().

The Standard Test Runner

The standard test runner in flutter_test_goldens is testGoldenScene().

void main() {
  testGoldenScene("my golden test", (tester) async {
    // TODO: implement golden test.
  });
}

The testGoldenScene() test runner wraps around Flutter's standard testWidgets() test runner, while making a few adjustments:

• Sets the devicePixelRatio to 1.0 to unify all test pixel densities, and reduce scaling artifacts.
• Sets the textScaleFactor to 1.0 to unify all test text scales, and reduce scaling artifacts.
• Loads app fonts so that labels and decorations around your goldens are rendered with a real font.

Platform Specific Test Runners

When writing golden tests, sometimes you may want to simulate a specific platform. For example, maybe you want to render a golden of your app with an iOS style UI, specifically. For this purpose, flutter_test_goldens provides per-platform test runners.

void main() {
  testGoldenSceneOnIOS("my iOS golden test", (tester) async {
    // TODO: implement golden test.
  });

  testGoldenSceneOnAndroid("my Android golden test", (tester) async {
    // TODO: implement golden test.
  });

  testGoldenSceneOnMac("my Mac golden test", (tester) async {
    // TODO: implement golden test.
  });

  testGoldenSceneOnWindow("my Windows golden test", (tester) async {
    // TODO: implement golden test.
  });

  testGoldenSceneOnLinux("my Linux golden test", (tester) async {
    // TODO: implement golden test.
  });
}

The implementation of the platform-specific test runners are nearly identical to testGoldenScene(), except they set the debugDefaultTargetPlatformOverride property to the given platform.

debugDefaultTargetPlatformOverride = TargetPlatform.macOS;

When the test completes, debugDefaultTargetPlatformOverride is reset to null.

You could implement this behavior yourself, within the standard testWidgets() runner, but these platform-specific test runners are provided as a convenient way to simulate a platform without repeating the platform configuration every time.