How to unit test WorkManager Worker

Question

How to unit test WorkManager Worker?

Here is sample Worker:

public class SampleWorker extends Worker {

    private static final String TAG = "SampleWorker";
    private static final String WORKER_TAG = "SAMPLE";

    static final String KEY_DATA_1 = "KEY_DATA_1";
    static final String KEY_DATA_2 = "KEY_DATA_2";


    public SampleWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
        super(context, workerParams);
    }

    public static WorkRequest createWorkRequest(String data1, String data2) {
        Constraints constraints = new Constraints.Builder()
                .setRequiredNetworkType(NetworkType.CONNECTED)
                .build();

        Data inputData = createData(data1, data2);

        return new OneTimeWorkRequest.Builder(SampleWorker.class)
                .setConstraints(constraints)
                .setInputData(inputData)
                .addTag(WORKER_TAG)
                .build();
    }

    static Data createData(String data1, String data2) {
        return new Data.Builder()
                .putString(KEY_DATA_1, data1)
                .putString(KEY_DATA_2, data2)
                .build();
    }

    @NonNull
    @Override
    public Result doWork() {
        try {
            Data inputData = getInputData();
            businessLogicHere(inputData.getString(KEY_DATA_1), inputData.getString(KEY_DATA_2));

            return Result.SUCCESS;
        } catch (Exception e) {
            Log.e(TAG, "doWork failed", e);
            return Result.FAILURE;
        }
    }

    private void businessLogicHere(String data1, String data2) {
        // no-op
    }
}

Answer 1

There is a testing library for WorkManager. Add the dependency:

androidTestImplementation "androidx.work:work-testing:$work_version"

Here's a simple example:

fun downloadFile() {
    val context = InstrumentationRegistry.getInstrumentation().targetContext
    val inputData = workDataOf("key" to "myValue")

    val worker = TestListenableWorkerBuilder<DownloadFileWorker>(context)
        .setInputData(inputData)
        .build()
    val result = worker.doWork()

    assertThat(result, Is(isEqualTo(ListenableWorker.Result.success())))
}

You can further configure the mocking with the TestListenableWorkerBuilder as needed.

Answer 2

With Work Manager alpha10 release a constructor was added with WorkerParameters so it is easier to pass input Data

Note: I created factory method in Worker class, so it is easier to read input data being passed and used in Worker.

Here is sample unit test:

  @RunWith(PowerMockRunner.class)
    @PrepareForTest({WorkerParameters.class})
    public class SampleWorkerTest {

    @Mock
    Context context;

    WorkerParameters workerParams;

    Data inputData;

    SampleWorker worker;

    @Before
    public void setUp() throws Exception {
        MockitoAnnotations.initMocks(this);
        workerParams = PowerMockito.mock(WorkerParameters.class);

        inputData = SampleWorker.createData("data one", "data two");
        when(workerParams.getInputData()).thenReturn(inputData);

        worker = new SampleWorker(context, workerParams);
    }

    @Test
    public void testCreateWorkRequestFactoryMethod() {
        WorkRequest workRequest = SampleWorker.createWorkRequest("data one", "data two");
        WorkSpec workSpec = workRequest.getWorkSpec();

        // verify constraints
        assertThat(workSpec.constraints.getRequiredNetworkType(), is(equalTo(NetworkType.CONNECTED)));

        // verify input data
        assertThat(workSpec.input.getString(SampleWorker.KEY_DATA_1), is(equalTo("data one")));
        assertThat(workSpec.input.getString(SampleWorker.KEY_DATA_2), is(equalTo("data two")));
    }

    @Test
    public void testDoWorkSuccess() {
        Worker.Result result = worker.doWork();

        // verify business logic here

        assertThat(result, is(equalTo(Worker.Result.SUCCESS)));
    }
}