unit-test-introduction.md

Intro

Use the test package provides the core framework for writing unit tests, and the flutter_test package provides additional utilities for testing widgets.

Getting started with test package

To add the test package as a dev dependency, run flutter pub add:

 $ flutter pub add dev:test

Create a sample Counter class for testing:

class Counter {
  int value = 0;

  void increment() => value++;

  void decrement() => value--;
}

Combine some unit tests with group:

import 'package:counter_app/counter.dart';
import 'package:test/test.dart';

void main() {
  group('Counter', () {
    test('value should start at 0', () {
      expect(Counter().value, 0);
    });

    test('value should be incremented', () {
      final counter = Counter();

      counter.increment();

      expect(counter.value, 1);
    });

    test('value should be decremented', () {
      final counter = Counter();

      counter.decrement();

      expect(counter.value, -1);
    });
  });
}

Run tests:

1. using IntelliJ or VSCode

• IntelliJ
  • Open the counter_test.dart file
  • Select the Run menu
  • Click the Run 'tests in counter_test.dart' option
  • Alternatively, use the appropriate keyboard shortcut for your platform.
• VSCode
  • Open the counter_test.dart file
  • Select the Run menu
  • Click the Start Debugging option
  • Alternatively, use the appropriate keyboard shortcut for your platform.

2. Terminal

$ flutter test test/counter_test.dart