Make sure some functions run on the background thread.

[levibostian]

I was creating integration tests the other day and when I tried to test observe() in an OnlineRepository subclass of mine, I was having a lot of exceptions.

Here is a gist of my test:

    @Test
    fun observeCachedData_data() {
        val foo = listOf(
                FooModel(id = 1)
        )
        insertFoo(foo)

        val body = GetFooResponse("", listOf())
        val result = Result.response(Response.success(body))
        `when`(service.getFoo(null)).thenReturn(
                Single.just(result).subscribeOn(Schedulers.io()) // Run on background thread as a DB save is triggered.
        )
        `when`(responseProcessor.process(result)).thenReturn(ResponseProcessor.ProcessedResult<GetFooResponse>(null, "", body))

        repository.loadDataRequirements = FooRepository.GetRequirements(null)
        repository.observe()
                .subscribeOn(Schedulers.io())
                .test()
                .awaitDone(500, TimeUnit.MILLISECONDS)
                .assertValue {
                    it.data!!.size == 1
                }
    }

Looking above, I was able to fix my test with the line: Single.just(result).subscribeOn(Schedulers.io()) // Run on background thread as a DB save is triggered. from my mock. I had to make sure that fetchFreshData() was called on a background thread. Why? Because in the OnlineRepository source code I notice that the thread that is subscribed on in fetchFreshData() determines what thread saveData() is called on.

This is not right. A subclass of OnlineRepository should always know what thread something is executed on.

[levibostian]

For this issue, I will be following the same patterns that Teller-iOS is using. The guarantee that certain functions of an OnlineRepository subclass are called by certain threads.

[levibostian]

Change added to this branch. Will be merged in soon.