java - Espresso 不等待 AsyncTask 完成

Question

根据 Espresso 文档，仪器测试应自动等待 AsyncTasks 完成。但它不起作用。我创建了这个简单的测试用例:

package foo.bar;

import android.os.AsyncTask;
import android.support.test.annotation.UiThreadTest;
import android.support.test.filters.LargeTest;
import android.support.test.rule.UiThreadTestRule;
import android.support.test.runner.AndroidJUnit4;
import android.util.Log;

import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;

import static org.junit.Assert.assertEquals;

@RunWith(AndroidJUnit4.class)
@LargeTest
public class ExampleInstrumentedTest {

    private static final String TAG = "ExampleInstrumentedTest";

    @Rule public UiThreadTestRule uiThreadTestRule = new UiThreadTestRule();

    @Test
    @UiThreadTest
    public void testAsyncTask() throws Throwable {
        Log.d(TAG, "testAsyncTask entry");
        uiThreadTestRule.runOnUiThread(() -> new AsyncTask<String, Void, Integer>() {
            @Override
            protected Integer doInBackground(String... params) {
                Log.d(TAG, "doInBackground() called with: params = [" + params + "]");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException ignored) {
                }
                return params.length;
            }

            @Override
            protected void onPostExecute(Integer integer) {
                Log.d(TAG, "onPostExecute() called with: integer = [" + integer + "]");
                assertEquals(3, (int) integer);
                throw new RuntimeException("this should fail the test");
            }
        }.execute("One", "two", "three"));
        Log.d(TAG, "testAsyncTask end");
    }
}

返回到 UI 线程时测试应该会失败，但它总是会成功。这是测试的 logcat 输出:

I/TestRunner: started: testAsyncTask(foo.bar.ExampleInstrumentedTest)
D/ExampleInstrumentedTest: testAsyncTask entry
D/ExampleInstrumentedTest: testAsyncTask end
I/TestRunner: finished: testAsyncTask(foo.bar.ExampleInstrumentedTest)
D/ExampleInstrumentedTest: doInBackground() called with: params = [[Ljava.lang.String;@8da3e9]

如您所见，测试甚至在后台方法执行之前就已完成。如何让测试等待它？

Answer 1

事实证明，Espresso 确实等待 AsyncTasks 完成但只有存在 View 交互时。

原因是 Espresso 在 UiController#loopMainThreadUntilIdle() 期间等待任务在每次 View 交互时在幕后自动调用的方法。因此，尽管我的测试不需要任何 View 或 Activity ，但我必须创建它们。

这就是工作测试现在的样子:

@RunWith(AndroidJUnit4.class)
@LargeTest
public class ExampleInstrumentedTest {

    private static final String TAG = "ExampleInstrumentedTest";

    @Rule public ActivityTestRule<TestingActivity> activityTestRule = new ActivityTestRule<>(
        TestingActivity.class, false, false);

    @Before
    public void setUp() throws Exception {
        activityTestRule.launchActivity(new Intent());
    }

    @Test
    public void testAsyncTask() throws Throwable {
        Log.d(TAG, "testAsyncTask entry");

        AsyncTask<String, Void, Integer> task = new AsyncTask<String, Void, Integer>() {

            @Override
            protected Integer doInBackground(String... params) {
                Log.d(TAG, "doInBackground() called with: params = [" + params + "]");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException ignored) {
                }
                return params.length;
            }

            @Override
            protected void onPostExecute(Integer integer) {
                Log.d(TAG, "onPostExecute() called with: integer = [" + integer + "]");
                assertEquals(3, (int) integer);
                throw new RuntimeException("this should fail the test");
            }
        };
        task.execute("One", "two", "three");
        Espresso.onView(withId(android.R.id.content)).perform(ViewActions.click());

        Log.d(TAG, "testAsyncTask end");
    }
}

最重要的新行是:Espresso.onView(withId(android.R.id.content)).perform(ViewActions.click()); 因为它会导致 Espresso 等待AsyncTask 后台操作完成。

TestingActivity 只是一个空 Activity :

public class TestingActivity extends Activity {

}