如何在Kotlin中使用JUnit Mockito测试/模拟API

Question

I am trying to wrote a Unit test in my Android application using kotlin. getPosts() get list of POSTS from https://jsonplaceholder.typicode.com/posts

I want to test this function comparing the count or any other way you suggest.

I am pretty new to this so any suggestions corrections will be very much helpful

Here is what I have tried so far. your help will be much appreciated.

R

@Singleton
class PostsRemoteDataSource @Inject constructor(
    private val postsService: PostsService
): PostsDataSource {
       override fun getAllPosts(): Flowable<List<PostEntity>> {
        return postsService.getPosts()
            .flatMap { posts ->
                Flowable.fromIterable(posts)
                    .take(10)
                    .toList().toFlowable()
            }
    }
}

PostService

interface PostsService {

    @GET("/posts")
    fun getPosts(): Flowable<List<PostEntity>>
}

Testcase

class PostsRemoteDataSourceTest {



    @Before
    fun init() {
        MockitoAnnotations.initMocks(this)
    }

    @Test
    fun getAllPosts() {
        val postService = mock(PostsService::class.java)
        val postsRemoteDataSource = PostsRemoteDataSource(postService)

        var mList = listOf<PostEntity>()

        Mockito.`when`(postService.getPosts()).thenReturn(Flowable.fromArray(mList))

        val allPosts = postsRemoteDataSource.getAllPosts()
        //PRETTY SURE THE LINE BELLOW IS WRONG I AM TRYING TO COMPARE THE 
       //COUNT BUT CANNOT GET appPosts.size as it is Flowable type
        assertEquals(allPosts , CoreMatchers.`is`(10))

    }
}

UPDATE

@Test
    fun getAllPosts() {
        val postService = mock(PostsService::class.java)
        val postsRemoteDataSource = PostsRemoteDataSource(postService)

        var mList = listOf<PostEntity>(
            PostEntity(1,1,"Title 1", "Body 1"),
            PostEntity(1,1,"Title 1", "Body 1")
        )

        Mockito.`when`(postService.getPosts()).thenReturn(Flowable.fromArray(mList))

        val subsciber = postsRemoteDataSource.getAllPosts().test()


        assertEquals(subsciber.assertValueCount(10) , 10)

    }
}

Error message when I run the test

    at io.reactivex.observers.BaseTestConsumer.fail(BaseTestConsumer.java:189)
    at io.reactivex.observers.BaseTestConsumer.assertValueCount(BaseTestConsumer.java:515)
    at com.rao.com.idealarchitecture.data.remote.PostsRemoteDataSourceTest.getAllPosts(PostsRemoteDataSourceTest.kt:41)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

Answer 1

Option 1

Use blockingFirst() to get data via a blocking call:

val allPosts = postsRemoteDataSource.getAllPosts().blockingFirst()
assertEquals(10, allPosts.size)

Note that making blocking calls on a Flowable is usually considered bad practice in production code, but it's safe to do in tests since your object under test is backed by a mock.

Option 2

Obtain a TestSubscriber by calling test() and assert on it:

val subscriber = postsRemoteDataSource.getAllPosts().test()
subscriber.assertValueCount(10)