scheduled_test 0.12.2

A package for writing readable tests of asynchronous behavior. This package works by building up a queue of asynchronous tasks called a "schedule", then executing those tasks in order. This allows the [...]

A package for writing readable tests of asynchronous behavior.

This package works by building up a queue of asynchronous tasks called a "schedule", then executing those tasks in order. This allows the tests to read like synchronous, linear code, despite executing asynchronously.

The scheduled_test package is built on top of the test package, and should be imported instead of test. It provides its own version of group(), test(), setUp(), and tearDown(), and re-exports most other APIs from test.

To schedule a task, call the schedule() function. For example:

import 'package:scheduled_test/scheduled_test.dart';

void main() {
  test('writing to a file and reading it back should work', () {
    schedule(() {
      // The schedule won't proceed until the returned Future has
      // completed.
      return new File("output.txt").writeAsString("contents");
    });

    schedule(() async {
      var contents = await new File("output.txt").readAsString();

      // The normal unittest matchers can still be used.
      expect(contents, equals("contents"));
    });
  });
}

Setting up and tearing down

The scheduled_test package defines its own setUp() method that works just like the one in test. Tasks can be scheduled in setUp(); they'll be run before the tasks scheduled by tests in that group. currentSchedule is also set in the setUp() callback.

Similarly, tasks to run after all the tests in the group can be scheduled using tearDown(). However, the best way to clean up after a test is to add callbacks to the onComplete queue. This queue will always run after the test, whether or not it succeeded. For example:

import 'package:scheduled_test/scheduled_test.dart';

void main() {
  var tempDir;
  setUp(() {
    schedule(() async {
      tempDir = await createTempDir();
    });

    currentSchedule.onComplete.schedule(() => deleteDir(tempDir));
  });

  // ...
}

Passing values between tasks

It's often useful to use values computed in one task in other tasks that are scheduled afterwards. There are two ways to do this. The most straightforward is just to define a local variable and assign to it. For example:

import 'package:scheduled_test/scheduled_test.dart';

void main() {
  test('computeValue returns 12', () {
    var value;

    schedule(() async {
      value = await computeValue();
    });

    schedule(() => expect(value, equals(12)));
  });
}

However, this doesn't scale well, especially when you start factoring out calls to schedule() into library methods. For that reason, schedule() returns a Future that will complete to the same value as the return value of the task. For example:

import 'package:scheduled_test/scheduled_test.dart';

void main() {
  test('computeValue returns 12', () {
    var valueFuture = schedule(() => computeValue());
    schedule(() {
      expect(valueFuture, completion(equals(12)));
    });
  });
}