Convert LooperExecutorTest in AppRTC Demo into JUnit test

LooperExecutorTest now uses Robolectric instead of being instrumentation
test. This allows the test to be run faster and easier.

Review-Url: https://codereview.webrtc.org/1989813002
Cr-Commit-Position: refs/heads/master@{#12825}

webrtc/examples/androidjunit/src/org/appspot/apprtc/util/LooperExecutorTest.java

@@ -0,0 +1,122 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.appspot.apprtc.util;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+import org.robolectric.shadows.ShadowLooper;
+
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.robolectric.Robolectric.shadowOf;
+
+@RunWith(RobolectricTestRunner.class)
+@Config(manifest = Config.NONE)
+public class LooperExecutorTest {
+  private final static int RUN_TIMES = 10;
+
+  @Mock private Runnable mockRunnable;
+  private LooperExecutor executor;
+
+  @Before
+  public void setUp() {
+    MockitoAnnotations.initMocks(this);
+    executor = new LooperExecutor();
+  }
+
+  @After
+  public void tearDown() {
+    executor.requestStop();
+    executePendingRunnables();
+  }
+
+  @Test
+  public void testExecute() {
+    executor.requestStart();
+
+    for (int i = 0; i < RUN_TIMES; i++) {
+      executor.execute(mockRunnable);
+    }
+
+    verifyNoMoreInteractions(mockRunnable);
+    executePendingRunnables();
+    verify(mockRunnable, times(RUN_TIMES)).run();
+  }
+
+  /**
+   * Test that runnables executed before requestStart are ignored.
+   */
+  @Test
+  public void testExecuteBeforeStart() {
+    executor.execute(mockRunnable);
+
+    executor.requestStart();
+    executePendingRunnables();
+
+    verifyNoMoreInteractions(mockRunnable);
+  }
+
+  /**
+   * Test that runnables executed after requestStop are not executed.
+   */
+  @Test
+  public void testExecuteAfterStop() {
+    executor.requestStart();
+    executor.requestStop();
+
+    executor.execute(mockRunnable);
+    executePendingRunnables();
+
+    verifyNoMoreInteractions(mockRunnable);
+  }
+
+  /**
+   * Test multiple requestStart calls are just ignored.
+   */
+  @Test
+  public void testMultipleStarts() {
+    executor.requestStart();
+    testExecute();
+  }
+
+  /**
+   * Test multiple requestStop calls are just ignored.
+   */
+  @Test
+  public void testMultipleStops() {
+    executor.requestStart();
+    executor.requestStop();
+    executor.requestStop();
+    executePendingRunnables();
+  }
+
+  /**
+   * Calls ShadowLooper's idle method in order to execute pending runnables.
+   */
+  private void executePendingRunnables() {
+    ShadowLooper shadowLooper = getShadowLooper();
+    shadowLooper.idle();
+  }
+
+  /**
+   * Get ShadowLooper of the executor thread.
+   */
+  private ShadowLooper getShadowLooper() {
+    return shadowOf(executor.getHandler().getLooper());
+  }
+}