Don't Mock Your Test Data

I found some strange condition when creating a test for a code with RxJava.

"Verify movie not empty and error" {
        Mockito.`when`(networkSource.getMovies())
                .then { mock<Single<List<Movie>>>() }

        tested.getMovies().test().also {
            it.assertNoErrors()
            it.assertComplete()
            it.assertValueCount(1)
        }
    }

The test is simply asserting my Single is running completely without error and exactly return one value. The problem is, my Single is neither completed or having an error. It also not returning any value.

java.lang.AssertionError: Not completed (latch = 1, values = 0, errors = 0, completions = 0)

After scratching my head for the rest of the day, it turns out my test code that was wrong. I stub one of my Single to return a mocked Single that doesn’t have behavior like the real Single at all.

So lesson learnt here:

1. The root of error in your test, maybe lies in your test, stub, mock logic, not your real code
2. Don’t mock your test data, use a real one. Then verify it.

You can find the full sample on my Github

Until next time. Cao ~ 👋