MutableLiveData 在 JUnitTest 中为 null

Question

我想写一个单元测试。因此我需要 MutableLiveData。我从一个非常基本的设置测试开始，但我无法实例化 MutableLiveData 对象。当我运行测试时，我总是空的。我必须嘲笑什么吗？有什么建议么？

@RunWith(MockitoJUnitRunner.class)
public class DefaultLiveDataTest {

    private static final int EXPECTED = 5;

    private final MutableLiveData<Integer> underTest = new MutableLiveData<>();


    @Test
    public void exampleTest() {

    underTest.setValue(EXPECTED); //underTest is Null
    assertEquals(underTest.getValue().intValue(), EXPECTED);

    }
}

java.lang.NullPointerException
at android.arch.core.executor.DefaultTaskExecutor.isMainThread(DefaultTaskExecutor.java:58)
at android.arch.core.executor.ArchTaskExecutor.isMainThread(ArchTaskExecutor.java:116)
at android.arch.lifecycle.LiveData.assertMainThread(LiveData.java:434)
at android.arch.lifecycle.LiveData.setValue(LiveData.java:279)
at android.arch.lifecycle.MutableLiveData.setValue(MutableLiveData.java:33)
at com.mypackage.DefaultLiveDataTest.test_that_live_data_has_default_value(DefaultLiveDataTest.java:22)

build.gradle

apply plugin: 'com.android.application'

android {
compileSdkVersion 27
defaultConfig {
    applicationId 'com.mypackage.title'
    minSdkVersion 16
    targetSdkVersion 27
    versionCode 1
    versionName '1.0'
    testInstrumentationRunner 'android.support.test.runner.AndroidJUnitRunner'
}

testOptions {
    unitTests.returnDefaultValues = true
}

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support:design:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.0.2'
implementation 'com.android.support:support-vector-drawable:27.1.1'
implementation 'android.arch.lifecycle:extensions:1.1.1'
implementation 'android.arch.lifecycle:viewmodel:1.1.1'
implementation 'android.arch.lifecycle:livedata:1.1.1'

annotationProcessor 'android.arch.lifecycle:compiler:1.1.1'
testImplementation 'junit:junit:4.12'
testImplementation 'org.mockito:mockito-core:1.10.19'
androidTestImplementation 'com.android.support.test:runner:1.0.1'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
annotationProcessor 'org.androidannotations:androidannotations:4.4.0'
implementation 'org.androidannotations:androidannotations-api:4.4.0'
compileOnly 'org.projectlombok:lombok:1.16.20'
annotationProcessor 'org.projectlombok:lombok:1.16.20'
}

Answer 1

看起来您缺少 android.arch.core:core-testing 依赖项。

testImplementation "android.arch.core:core-testing:1.1.1"

这允许您在测试中使用 InstantTaskExecutorRule，这将摆脱 isMainThread 调用。

https://developer.android.com/reference/android/arch/core/executor/testing/InstantTaskExecutorRule.html

@Rule
public InstantTaskExecutorRule instantTaskExecutorRule = new InstantTaskExecutorRule();

Answer 2

添加一个执行者InstantTaskExecutorRule()作为测试成员class

A JUnit Test Rule that swaps the background executor used by the Architecture Components with a different one which executes each task synchronously. You can use this rule for your host side tests that use Architecture Components.

//@RunWith(JUnit4::class)   // For JUnit4
@ExtendWith(InstantExecutorExtension::class)   // For JUnit5
class FilterViewModelTest {

    @Rule @JvmField
    val instantTaskExecutorRule = InstantTaskExecutorRule()

    @Test
    fun test() {
        //Here you don't ask if isMainThread
    }
}

build.gradle(:手机)

android {
    //...
    dependencies {
        //...
        testImplementation 'androidx.arch.core:core-testing:2.1.0'
        androidTestImplementation 'androidx.arch.core:core-testing:2.1.0'
    }
}

GL

InstantTaskExecutorRule

Answer 3

我有这个错误并通过添加 InstantTaskExecutorRule 解决了它：

private lateinit var contactProfileViewModel: ContactProfileViewModel

private val getStatusesForContact: GetStatusesForContact = mockk(relaxed = true)
private val getStory: GetUserLastStory = mockk(relaxed = true)
private val successStatusesCaptor = slot<((List<StatusDomain>) -> Unit)>()
private val successStoryCaptor = slot<((List<StoryDomain>) -> Unit)>()

@get:Rule
val rule: TestRule = InstantTaskExecutorRule()

@Before
fun setUp(){
    contactProfileViewModel = ContactProfileViewModel(getStatusesForContact, getStory)
}

MutableLiveData 在 JUnitTest 中为 null

MutableLiveData is null in JUnitTest

testing

android

android-testing

android-livedata

androidx

build.gradle(:手机)