Mock LifecycleOwner

private static LifecycleOwner mockLifecycleOwner() {
    LifecycleOwner owner = mock(LifecycleOwner.class);
    LifecycleRegistry lifecycle = new LifecycleRegistry(owner);
    lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_RESUME);
    when(owner.getLifecycle()).thenReturn(lifecycle);
    return owner;
}

Mock Observer

@SuppressWarnings("unchecked")
private static <T> Observer<T> mockObserver() {
    return (Observer<T>) Mockito.mock(Observer.class);
}

在测试的类添加Rule

@Rule
public TestRule rule = new InstantTaskExecutorRule();

添加依赖

// LiveData Test
dependencies {
    // Test helpers for LiveData
    androidTestImplementation "android.arch.core:core-testing:$lifecycle_version"
}

// Mockito
dependencies {
    def mockito_version = "2.23.4"
    testImplementation "org.mockito:mockito-core:$mockito_version"
    androidTestImplementation "org.mockito:mockito-android:$mockito_version"
}