Add unit test to RenderSynchronizer

Bug: b/307672498
Change-Id: Ia50f514ff9ecbd273953fc1eab55340b75728a4f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/325185
Commit-Queue: Linus Nilsson <lnilsson@webrtc.org>
Reviewed-by: Zoé Lepaul <xalep@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41094}

sdk/android/BUILD.gn

@@ -1720,6 +1720,7 @@ if (is_android) {
       "tests/src/org/webrtc/HardwareVideoEncoderTest.java",
       "tests/src/org/webrtc/IceCandidateTest.java",
       "tests/src/org/webrtc/RefCountDelegateTest.java",
+      "tests/src/org/webrtc/RenderSynchronizerTest.java",
       "tests/src/org/webrtc/ScalingSettingsTest.java",
       "tests/src/org/webrtc/audio/LowLatencyAudioBufferManagerTest.java",
     ]

sdk/android/tests/src/org/webrtc/RenderSynchronizerTest.java

@@ -0,0 +1,123 @@
+/*
+ *  Copyright 2023 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.webrtc;
+
+import static java.lang.Math.ceil;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import androidx.test.runner.AndroidJUnit4;
+import java.time.Duration;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InOrder;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.annotation.Config;
+import org.robolectric.shadows.ShadowLooper;
+import org.robolectric.shadows.ShadowChoreographer;
+
+@RunWith(AndroidJUnit4.class)
+@Config(manifest = Config.NONE)
+public class RenderSynchronizerTest {
+
+  private static final Duration FRAME_DELAY = Duration.ofMillis(16);
+  private static final float DEFAULT_FRAME_RATE = 30f;
+
+  @Mock private RenderSynchronizer.Listener mockListener;
+  private RenderSynchronizer renderSynchronizer;
+  private Duration refreshDelay;
+  private float frameRate;
+
+  @Before
+  public void setUp() {
+    MockitoAnnotations.initMocks(this);
+    ShadowChoreographer.setPaused(true);
+  }
+
+  private void init(float displayRefreshRate, float renderFrameRate) {
+    refreshDelay = Duration.ofMillis((long)ceil(1000 / displayRefreshRate));
+    frameRate = renderFrameRate;
+
+    ShadowChoreographer.setFrameDelay(refreshDelay);
+    renderSynchronizer = new RenderSynchronizer(renderFrameRate);
+    renderSynchronizer.registerListener(mockListener);
+  }
+
+  @Test
+  public void renderWindowOpensOnFirstFrame() {
+    init(/* displayRefreshRate= */60f, /* renderFrameRate= */30f);
+
+    advanceOneRefreshCycle();
+    verify(mockListener).onRenderWindowOpen();
+  }
+
+  @Test
+  public void doubleDisplayRefreshRate() {
+    init(/* displayRefreshRate= */60f, /* renderFrameRate= */30f);
+
+    InOrder inOrder = inOrder(mockListener);
+    for (int i = 0; i < 10; ++i) {
+      advanceOneRefreshCycle();
+      inOrder.verify(mockListener).onRenderWindowOpen();
+
+      advanceOneRefreshCycle();
+      inOrder.verify(mockListener).onRenderWindowClose();
+    }
+  }
+
+  @Test
+  public void trippleRefreshRate() {
+    init(/* displayRefreshRate= */90f, /* renderFrameRate= */30f);
+    InOrder inOrder = inOrder(mockListener);
+    for (int i = 0; i < 10; ++i) {
+      advanceOneRefreshCycle();
+      inOrder.verify(mockListener).onRenderWindowOpen();
+
+      advanceOneRefreshCycle();
+      inOrder.verify(mockListener).onRenderWindowClose();
+
+      advanceOneRefreshCycle();
+      // No action expected, window stays closed/
+    }
+  }
+
+  @Test
+  public void equalRefreshRate() {
+    init(/* displayRefreshRate= */30f, /* renderFrameRate= */30f);
+    for (int i = 0; i < 10; ++i) {
+      advanceOneRefreshCycle();
+    }
+    verify(mockListener, times(10)).onRenderWindowOpen();
+    verify(mockListener, times(0)).onRenderWindowClose();
+  }
+
+  @Test
+  public void halfRefreshRate() {
+    init(/* displayRefreshRate= */30f, /* renderFrameRate= */60f);
+    for (int i = 0; i < 10; ++i) {
+      advanceOneRefreshCycle();
+    }
+    verify(mockListener, times(10)).onRenderWindowOpen();
+    verify(mockListener, times(0)).onRenderWindowClose();
+  }
+
+  private void advanceOneRefreshCycle() {
+    advanceBy(refreshDelay);
+  }
+
+  private void advanceBy(Duration duration) {
+    ShadowLooper.idleMainLooper(duration.toMillis(), MILLISECONDS);
+  }
+}