How to use TestScheduler in RxJava

Question

How should I use RxJava\'s TestScheduler? I come from a .NET background but the TestScheduler in RxJava does not seem to work the same way as the t

Answer 1

you have some class:

public class SomeClass {
  public void someMethod() {
    Observable tick = Observable.interval(1, TimeUnit.SECONDS);
    contactsRepository.find(index)
      .buffer(MAX_CONTACTS_FETCH)
      .zipWith(tick, new Func2, Long, List>() {
        @Override
        public List call(List contactList, Long aLong) {
          return contactList;
        }
      }).subscribe()
  }
}

Look up [Observable.interval][1] in the docs and you will see it operates on the computation scheduler, so lets override that in our test.

public class SomeClassTest {
  private TestScheduler testScheduler;

  @Before
  public void before() {
    testScheduler = new TestScheduler();
    // set calls to Schedulers.computation() to use our test scheduler
    RxJavaPlugins.setComputationSchedulerHandler(ignore -> testScheduler);
  }

  @After
  public void after() {
    // reset it
    RxJavaPlugins.setComputationSchedulerHandler(null);
  }

  @Test
  public void test() {
    SomeClass someInstance = new SomeClass();
    someInstance.someMethod();

    // advance time manually
    testScheduler.advanceBy(1, TimeUnit.SECONDS);
  }

This solution is an improvement to the accepted answer as the quality, integrity and simplicity of the production code is maintained.