test method

@isTest void test(String description, Tester<T> body, { String? testOn, Timeout? timeout, dynamic skip, dynamic tags, Map<String, dynamic>? onPlatform, int? retry, })

Executes the given body with a bunch of parameters, trying to break it.

Implementation

@isTest
void test(
  String description,
  Tester<T> body, {
  String? testOn,
  test_package.Timeout? timeout,
  dynamic skip,
  dynamic tags,
  Map<String, dynamic>? onPlatform,
  int? retry,
}) {
  final stats = Statistics();

  /// Explores the input space for inputs that break the property. This works
  /// by gradually increasing the size. Returns the first value where the
  /// property is broken or null if no value was found.
  Future<Shrinkable<T>?> explorePhase() async {
    var count = 0;
    var size = explore.initialSize;

    while (count < explore.numRuns) {
      stats.exploreCounter++;
      final input = generator(explore.random, size.ceil());
      if (!await succeeds(body, input.value)) {
        return input;
      }

      count++;
      size += explore.speed;
    }
    return null;
  }

  /// Shrinks the given value repeatedly. Returns the shrunk input.
  Future<T> shrinkPhase(Shrinkable<T> initialErrorInducingInput) async {
    var input = initialErrorInducingInput;

    outer:
    while (true) {
      for (final shrunkInput in input.shrink()) {
        stats.shrinkCounter++;
        if (!await succeeds(body, shrunkInput.value)) {
          input = shrunkInput;
          continue outer;
        }
      }
      break;
    }
    return input.value;
  }

  test_package.test(
    '$description (testing ${explore.numRuns} '
    '${explore.numRuns == 1 ? 'input' : 'inputs'})',
    () async {
      final errorInducingInput = await explorePhase();
      if (errorInducingInput == null) return;

      final shrunkInput = await shrinkPhase(errorInducingInput);
      print('Tested ${stats.exploreCounter} '
          '${stats.exploreCounter == 1 ? 'input' : 'inputs'}, shrunk '
          '${stats.shrinkCounter} ${stats.shrinkCounter == 1 ? 'time' : 'times'}.'
          '\nFailing for input: $shrunkInput');
      final output = body(shrunkInput); // This should fail the test again.

      throw PropertyTestNotDeterministic(shrunkInput, output);
    },
    testOn: testOn,
    timeout: timeout,
    skip: skip,
    tags: tags,
    onPlatform: onPlatform,
    retry: retry,
  );
}