Testing Skill

This skill defines how to write effective, meaningful Flutter and Dart tests.

1. Test Validity

Before writing or accepting a test, ask:

"Can this test actually fail if the real code is broken?"

Avoid tests that only confirm mocked/fake behavior that doesn't reflect real logic.
Avoid tests that confirm behavior guaranteed by the language, the standard library, or trivially obvious code that cannot fail unless the environment is broken.
Every test should be capable of catching a real regression.

Always use group() in test files — even when there is only one test. Name the group after the class under test:

group('Counter', () {
  test('value should start at 0', () {
    final counter = Counter();
    expect(counter.value, 0);
  });
});

Name test cases using "should" to clearly describe the expected behavior:

test('should emit updated list when item is added', () { ... });
test('should throw ArgumentError when input is negative', () { ... });