Enhanced tests for interop / countrylist (Exposureapp-2733, EXPOSUREAPP-2744) (#1255)

* test enhancement for interop and countrylist, added liveDataTestExtension

* better test naming, removed one assert

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>

Corona-Warn-App/src/test/java/de/rki/coronawarnapp/ui/interoperability/InteroperabilityConfigurationFragmentViewModelTest.kt

+package de.rki.coronawarnapp.ui.interoperability
+
+import androidx.lifecycle.MutableLiveData
+import de.rki.coronawarnapp.storage.interoperability.InteroperabilityRepository
+import io.mockk.every
+import io.mockk.impl.annotations.MockK
+import io.mockk.junit5.MockKExtension
+import io.mockk.verify
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.junit.jupiter.api.extension.Extensions
+import testhelpers.extensions.InstantExecutorExtension
+import testhelpers.extensions.getOrAwaitValue
+
+@Extensions(
+    ExtendWith(MockKExtension::class),
+    ExtendWith(InstantExecutorExtension::class)
+)
+class InteroperabilityConfigurationFragmentViewModelTest {
+
+    @MockK(relaxUnitFun = true)
+    lateinit var interoperabilityRepository: InteroperabilityRepository
+
+    private lateinit var interoperabilityConfigurationFragmentViewModel: InteroperabilityConfigurationFragmentViewModel
+
+    private val countryListLiveData = MutableLiveData<List<String>>(listOf())
+
+    @BeforeEach
+    fun setupFreshViewModel() {
+        every { interoperabilityRepository.countryList } returns countryListLiveData
+        interoperabilityConfigurationFragmentViewModel =
+            InteroperabilityConfigurationFragmentViewModel(interoperabilityRepository)
+    }
+
+    @Test
+    fun countryListIsEmptyIfRepositoryReturnsNoData() {
+        val countryList =
+            interoperabilityConfigurationFragmentViewModel.countryList.getOrAwaitValue()
+
+        assertTrue(countryList.isEmpty())
+    }
+
+    @Test
+    fun testFetchCountryList() {
+        val countryListFetched = listOf(
+            "DE", "UK", "FR", "IT", "ES", "PL", "RO", "NL",
+            "BE", "CZ", "SE", "PT", "HU", "AT", "CH", "BG", "DK", "FI", "SK",
+            "NO", "IE", "HR", "SI", "LT", "LV", "EE", "CY", "LU", "MT", "IS"
+        )
+
+        interoperabilityRepository.getAllCountries()
+        countryListLiveData.value = countryListFetched
+
+        val countryList =
+            interoperabilityConfigurationFragmentViewModel.countryList.getOrAwaitValue()
+
+        assertEquals(countryList.size, countryListFetched.size)
+        assertTrue(countryList == countryListFetched)
+        verify { interoperabilityRepository.getAllCountries() }
+    }
+
+    @Test
+    fun testBackPressButton() {
+        interoperabilityConfigurationFragmentViewModel.onBackPressed()
+
+        assertTrue(interoperabilityConfigurationFragmentViewModel.navigateBack.getOrAwaitValue())
+    }
+}

Corona-Warn-App/src/test/java/testhelpers/extensions/LiveDataTestExtension.kt

+package testhelpers.extensions
+
+/**
+ * Thanks to https://github.com/android/architecture-components-samples/blob/master/LiveDataSample/app/src/test/java/com/android/example/livedatabuilder/util/LiveDataTestUtil.kt
+ */
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.Observer
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
+
+/**
+ * Gets the value of a [LiveData] or waits for it to have one, with a timeout.
+ *
+ * Use this extension from host-side (JVM) tests. It's recommended to use it alongside
+ * `InstantTaskExecutorRule` or a similar mechanism to execute tasks synchronously.
+ */
+fun <T> LiveData<T>.getOrAwaitValue(
+    time: Long = 2,
+    timeUnit: TimeUnit = TimeUnit.SECONDS,
+    afterObserve: () -> Unit = {}
+): T {
+    var data: T? = null
+    val latch = CountDownLatch(1)
+    val observer = object : Observer<T> {
+        override fun onChanged(o: T?) {
+            data = o
+            latch.countDown()
+            this@getOrAwaitValue.removeObserver(this)
+        }
+    }
+    this.observeForever(observer)
+
+    afterObserve.invoke()
+
+    // Don't wait indefinitely if the LiveData is not set.
+    if (!latch.await(time, timeUnit)) {
+        this.removeObserver(observer)
+        throw TimeoutException("LiveData value was never set.")
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    return data as T
+}
+
+/**
+ * Observes a [LiveData] until the `block` is done executing.
+ */
+fun <T> LiveData<T>.observeForTesting(block: () -> Unit) {
+    val observer = Observer<T> { }
+    try {
+        observeForever(observer)
+        block()
+    } finally {
+        removeObserver(observer)
+    }
+}