JUnitTest中的MutableLiveData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,我总是为空.我必须嘲笑任何东西吗？有什么建议？

@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)

的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

看起来你缺少android.arch.core:核心测试依赖.

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

这允许您在测试中使用InstantTaskExecutorRule,这将消除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 executorInstantTaskExecutorRule()作为 Test 类的成员

一种 JUnit 测试规则，它将架构组件使用的后台执行程序与同步执行每个任务的不同的后台执行程序交换。您可以将此规则用于使用架构组件的主机端测试。

@RunWith(JUnit4::class)
class FilterViewModelTest {

    @Rule @JvmField
    val instantTaskExecutorRule = InstantTaskExecutorRule()

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

build.gradle(:mobile)

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

GL

即时任务执行器规则

Answer 3

我遇到了这个错误，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)
}