Testing with package:test

Build Testing with package:test in vertical slices that separate library boundaries, domain logic, I/O, and tests. Cover normal, null, empty, invalid, async-error, and cancellation cases with repeatable tests.

Build a Complete Mental Model

Build Testing with package:test in vertical slices that separate library boundaries, domain logic, I/O, and tests. Cover normal, null, empty, invalid, async-error, and cancellation cases with repeatable tests.

Apply It in Modern Dart

Run and test an original Testing with package:test example with null, empty, boundary, invalid, async-error, and cancellation cases. Use dart format, dart analyze, and dart test, and verify Future or Stream subscriptions and isolate boundaries where relevant.

After This Lesson

• Explain nullability, mutability, and async contracts
• Write an example that passes dart analyze
• Test a failure or async case

import 'package:test/test.dart';

int total(Iterable<int> values) => values.fold(0, (a, b) => a + b);

void main() {
  group('total', () {
    test('handles empty and populated values', () {
      expect(total([]), 0);
      expect(total([1, 2, 3]), 6);
    });
  });
}

All tests passed!

Dart testing — Dart