dart-test-fundamentals

Dart Test Fundamentals

When to use this skill

Use this skill when:

• Writing new test files.
• structuring test suites with group.
• Configuring test execution via dart_test.yaml.
• Understanding test lifecycle methods.

Core Concepts

1. Test Structure (test and group)

• test: The fundamental unit of testing.

  test('description', () {
    // assertions
  });
  

• group: Used to organize tests into logical blocks.

  • Groups can be nested.
  • Descriptions are concatenated (e.g., "Group Description Test Description").
  • Helps scope setUp and tearDown calls.
  • Naming: Use PascalCase for groups that correspond to a class name (e.g., group('MyClient', ...)).
  • Avoid Single Groups: Do not wrap all tests in a file with a single group call if it's the only one.

• Naming Tests:

  • Avoid redundant "test" prefixes.
  • Include the expected behavior or outcome in the description (e.g., 'throws StateError' or 'adds API key to URL').
  • Descriptions should read well when concatenated with their group name.

• Named Parameters Placement:

  • For test and group calls, place named parameters (e.g., testOn, timeout, skip) immediately after the description string, before the callback closure. This improves readability by keeping the test logic last.

    test('description', testOn: 'vm', () {
      // assertions
    });
    

2. Lifecycle Methods (setUp, tearDown)

• setUp: Runs before every test in the current group (and nested groups).
• tearDown: Runs after every test in the current group.
• setUpAll: Runs once before any test in the group.
• tearDownAll: Runs once after all tests in the group.

Best Practice:

• Use setUp for resetting state to ensure test isolation.
• Avoid sharing mutable state between tests without resetting it.

3. Configuration (dart_test.yaml)

The dart_test.yaml file configures the test runner. Common configurations include: