Android App From Scratch Part 5 — Instrumentation Tests

In this tutorial series, I will try to create an RSS Reader app step by step. Through this series I will explain:

1. How to use Model-View-Presenter in an Android App
2. Implementing must have libraries
3. Implementing App Logic
4. Creating unit tests with JUnit
5. Creating Android Instrumentations tests
6. Continuous Integration with Travis-CI

The cost of instrumentation tests is much more than JUnit tests. Because a device/emulator is needed to run instrumentation tests. If there is a network operation, UI tests get more complicated and slower. So try to use JUnit tests instead of instrumentation tests.

I will write instrumentation tests with Espresso and use mock responses to make UI tests faster. Espresso will not wait for the network operations. Also, I will test both success and error cases.

There’s a builtin espresso recorder tool in Android Studio. It works but generates spaghetti code. I use it once before writing tests. Then clean most of the boilerplate code.

Before reading the rest of this post, I highly recommend you to read Jake Wharton’s testing robots.

Espresso Robot Pattern in Kotlin

With the test cases I will verify that:

• ViewPager has an adapter and fragments inside viewPager
• RecyclerView has an adapter and item count is as expected
• SwipeRefreshLayout is working and loading data
• An error message is shown is fetching RSS fails

Test rule is set to prevent activity launch as soon as tests start.

@LargeTest
@RunWith(AndroidJUnit4::class)
class AllTests {

    @get:Rule
    var rule = ActivityTestRule(MainActivity::class.java,
            false,
            false)
}

Creating mock repositories with mock data.

class MockMainRepository : MainRepository {

    override fun parseFeeds() = FEEDS

    companion object {
        val FEEDS = listOf(
                Feed(0, "title1", MockRssRepository.SUCCESS_URL),
                Feed(1, "title2", MockRssRepository.ERROR_URL)
        )
    }
}

For the first time fetchRss() method is called reponse contains 5 items. When this method called again it contains 10 items. This behaviour is for testing swipe refresh layout.

class MockRssRepository : RssRepository {

    private var lastIndex = 1
    private val count = 5

    override fun fetchRss(url: String, listener: RssResponseListener) {
        when (url) {
            SUCCESS_URL -> listener.getResponse(url, RssResponse.success(ITEMS.subList(0, lastIndex++ * count)))
            ERROR_URL -> listener.getResponse(url, RssResponse.error(Error.generic()))
        }
    }

    companion object {
        const val SUCCESS_URL = "https://github.com"
        const val ERROR_URL = "error_url"

        val ITEMS = listOf(
                RssItem().apply {
                    title = "title0"
                    link = SUCCESS_URL
                }, ....
   
        )
    }

}

I override NetworkModule to inject mock objects.

class MockNetworkModule : NetworkModule() {

    @Provides
    @Singleton
    override fun provideRssRepository(service: RssService): RssRepository = MockRssRepository()

    @Provides
    @Singleton
    override fun provideMainRepository(app: Application): MainRepository = MockMainRepository()
}

Before tests start mock dependencies are injected.

@Before
fun setup() {
    NewsApp.setComponent(DaggerAppComponent.builder()
            .appModule(AppModule(NewsApp.instance))
            .networkModule(MockNetworkModule())
            .build())

    val intent = Intent()
    rule.launchActivity(intent)
}

Now tests can be run.

@Test
fun loadViewPagerTest() {
    news {
        checkViewPagerItems(rule)
        swipeLeft()
        swipeRight()
    }
}

Here are the details of checkViewPagerItems()

fun checkViewPagerItems(rule: ActivityTestRule<MainActivity>) {
    val viewPager = rule.activity.findViewById(R.id.viewPager) as ViewPager
    Assert.assertNotNull(viewPager)
    Assert.assertNotNull(viewPager.adapter)
    Assert.assertTrue(MockMainRepository.FEEDS.size == viewPager.adapter?.count)
}

Other test cases:

@Test
fun recyclerViewItemsTest() {
    news {
        checkRecyclerViewItemCount(rule, 5)
        checkRecyclerViewItemContent()
    }
}

@Test
fun swipeRefreshTest() {
    news {
        checkRecyclerViewItemCount(rule, 5)
        swipeDown()
        checkSwipeRefresh(rule)
        checkRecyclerViewItemCount(rule, 10)
    }
}

@Test
fun loadFailed() {
    news {
        swipeLeft()
        checkErrorTextView()
    }
}

You can check my GitHub repo for the full source code:

faruktoptas/news-mvp

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