FakeAsync class

A mechanism to make time-dependent units testable.

Test code can be passed as a callback to run, which causes it to be run in a Zone which fakes timer and microtask creation, such that they are run during calls to elapse which simulates the asynchronous passage of time.

The synchronous passage of time (blocking or expensive calls) can also be simulated using elapseBlocking.

To allow the unit under test to tell time, it can receive a Clock as a dependency, and default it to const Clock() in production, but then use clock in test code.

Example:

test('testedFunc', () {
  new FakeAsync().run((async) {
    testedFunc(clock: async.getClock(initialTime));
    async.elapse(duration);
    expect(...)
  });
});