PostRepositoryImplTest.kt

class PostRepositoryImplTest {

    private lateinit var repository: PostRepositoryImpl

    private val mockCacheDataSource: PostCacheDataSource = mock()
    private val mockRemoteDataSource: PostRemoteDataSource = mock()

    private val postId = post.id

    private val cacheItem = post.copy(title = "cache")
    private val remoteItem = post.copy(title = "remote")

    private val cacheList = listOf(cacheItem)
    private val remoteList = listOf(remoteItem)

    private val cacheThrowable = Throwable()
    private val remoteThrowable = Throwable()

    @Before
    fun setUp() {
        repository = PostRepositoryImpl(mockCacheDataSource, mockRemoteDataSource)
    }

    @Test
    fun `get posts cache success`() {
        // given
        whenever(mockCacheDataSource.get()).thenReturn(Single.just(cacheList))

        // when
        val test = repository.get(false).test()

        // then
        verify(mockCacheDataSource).get()
        test.assertValue(cacheList)
    }

    @Test
    fun `get posts cache fail fallback remote succeeds`() {
        // given
        whenever(mockCacheDataSource.get()).thenReturn(Single.error(cacheThrowable))
        whenever(mockRemoteDataSource.get()).thenReturn(Single.just(remoteList))
        whenever(mockCacheDataSource.set(remoteList)).thenReturn(Single.just(remoteList))

        // when
        val test = repository.get(false).test()

        // then
        verify(mockCacheDataSource).get()
        verify(mockRemoteDataSource).get()
        verify(mockCacheDataSource).set(remoteList)
        test.assertValue(remoteList)
    }

    @Test
    fun `get posts cache fail fallback remote fails`() {
        // given
        whenever(mockCacheDataSource.get()).thenReturn(Single.error(cacheThrowable))
        whenever(mockRemoteDataSource.get()).thenReturn(Single.error(remoteThrowable))

        // when
        val test = repository.get(false).test()

        // then
        verify(mockCacheDataSource).get()
        verify(mockRemoteDataSource).get()
        test.assertError(remoteThrowable)
    }

    @Test
    fun `get posts remote success`() {
        // given
        whenever(mockRemoteDataSource.get()).thenReturn(Single.just(remoteList))
        whenever(mockCacheDataSource.set(remoteList)).thenReturn(Single.just(remoteList))

        // when
        val test = repository.get(true).test()

        // then
        verify(mockRemoteDataSource).get()
        verify(mockCacheDataSource).set(remoteList)
        test.assertValue(remoteList)
    }

    @Test
    fun `get posts remote fail`() {
        // given
        whenever(mockRemoteDataSource.get()).thenReturn(Single.error(remoteThrowable))

        // when
        val test = repository.get(true).test()

        // then
        verify(mockRemoteDataSource).get()
        test.assertError(remoteThrowable)
    }
}