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Testing Track Selection Mapping Implementation in SmartTube

This test suite validates the MappingTrackSelector component in ExoPlayer, focusing on proper mapping of video and audio track groups to their respective renderers. It ensures correct track selection and handling of media formats in the SmartTube application.

Test Coverage Overview

The test suite provides comprehensive coverage of track selection and mapping functionality:

  • Basic video and audio track group mapping to renderers
  • Reverse order renderer mapping verification
  • Multiple track group handling of same media type
  • Format support and adaptation testing

Implementation Analysis

The testing approach utilizes JUnit with AndroidJUnit4 runner for Android-specific testing. The implementation employs fake renderers and track groups to simulate real media components, using mock objects for isolated testing of mapping logic.

Key patterns include:
  • Fake implementations for renderer capabilities
  • Track group array manipulation
  • Format handling verification

Technical Details

Testing infrastructure includes:

  • JUnit test framework with AndroidJUnit4 runner
  • ExoPlayer core components for media handling
  • Custom FakeMappingTrackSelector for verification
  • Mock implementations of RendererCapabilities
  • TrackGroup and Format utilities for media format testing

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

  • Isolated component testing using mock objects
  • Clear test case organization and naming
  • Comprehensive edge case coverage
  • Proper setup and initialization in @BeforeClass
  • Explicit verification of expected behaviors

yuliskov/smarttube

exoplayer-amzn-2.10.6/library/core/src/test/java/com/google/android/exoplayer2/trackselection/MappingTrackSelectorTest.java

            
/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.android.exoplayer2.trackselection;

import static com.google.common.truth.Truth.assertThat;

import android.util.Pair;
import androidx.test.ext.junit.runners.AndroidJUnit4;
import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.ExoPlaybackException;
import com.google.android.exoplayer2.Format;
import com.google.android.exoplayer2.RendererCapabilities;
import com.google.android.exoplayer2.RendererConfiguration;
import com.google.android.exoplayer2.Timeline;
import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
import com.google.android.exoplayer2.source.TrackGroup;
import com.google.android.exoplayer2.source.TrackGroupArray;
import com.google.android.exoplayer2.testutil.FakeTimeline;
import com.google.android.exoplayer2.util.MimeTypes;
import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;

/** Unit tests for {@link MappingTrackSelector}. */
@RunWith(AndroidJUnit4.class)
public final class MappingTrackSelectorTest {

  private static final RendererCapabilities VIDEO_CAPABILITIES =
      new FakeRendererCapabilities(C.TRACK_TYPE_VIDEO);
  private static final RendererCapabilities AUDIO_CAPABILITIES =
      new FakeRendererCapabilities(C.TRACK_TYPE_AUDIO);
  private static final RendererCapabilities[] RENDERER_CAPABILITIES = new RendererCapabilities[] {
      VIDEO_CAPABILITIES, AUDIO_CAPABILITIES
  };
  private static final TrackGroup VIDEO_TRACK_GROUP = new TrackGroup(
      Format.createVideoSampleFormat("video", MimeTypes.VIDEO_H264, null, Format.NO_VALUE,
          Format.NO_VALUE, 1024, 768, Format.NO_VALUE, null, null));
  private static final TrackGroup AUDIO_TRACK_GROUP = new TrackGroup(
      Format.createAudioSampleFormat("audio", MimeTypes.AUDIO_AAC, null, Format.NO_VALUE,
          Format.NO_VALUE, 2, 44100, null, null, 0, null));
  private static final TrackGroupArray TRACK_GROUPS = new TrackGroupArray(
      VIDEO_TRACK_GROUP, AUDIO_TRACK_GROUP);
  private static final Timeline TIMELINE = new FakeTimeline(/* windowCount= */ 1);

  private static MediaPeriodId periodId;

  @BeforeClass
  public static void setUpBeforeClass() {
    periodId = new MediaPeriodId(TIMELINE.getUidOfPeriod(/* periodIndex= */ 0));
  }

  /**
   * Tests that the video and audio track groups are mapped onto the correct renderers.
   */
  @Test
  public void testMapping() throws ExoPlaybackException {
    FakeMappingTrackSelector trackSelector = new FakeMappingTrackSelector();
    trackSelector.selectTracks(RENDERER_CAPABILITIES, TRACK_GROUPS, periodId, TIMELINE);
    trackSelector.assertMappedTrackGroups(0, VIDEO_TRACK_GROUP);
    trackSelector.assertMappedTrackGroups(1, AUDIO_TRACK_GROUP);
  }

  /**
   * Tests that the video and audio track groups are mapped onto the correct renderers when the
   * renderer ordering is reversed.
   */
  @Test
  public void testMappingReverseOrder() throws ExoPlaybackException {
    FakeMappingTrackSelector trackSelector = new FakeMappingTrackSelector();
    RendererCapabilities[] reverseOrderRendererCapabilities = new RendererCapabilities[] {
        AUDIO_CAPABILITIES, VIDEO_CAPABILITIES};
    trackSelector.selectTracks(reverseOrderRendererCapabilities, TRACK_GROUPS, periodId, TIMELINE);
    trackSelector.assertMappedTrackGroups(0, AUDIO_TRACK_GROUP);
    trackSelector.assertMappedTrackGroups(1, VIDEO_TRACK_GROUP);
  }

  /**
   * Tests video and audio track groups are mapped onto the correct renderers when there are
   * multiple track groups of the same type.
   */
  @Test
  public void testMappingMulti() throws ExoPlaybackException {
    FakeMappingTrackSelector trackSelector = new FakeMappingTrackSelector();
    TrackGroupArray multiTrackGroups = new TrackGroupArray(VIDEO_TRACK_GROUP, AUDIO_TRACK_GROUP,
        VIDEO_TRACK_GROUP);
    trackSelector.selectTracks(RENDERER_CAPABILITIES, multiTrackGroups, periodId, TIMELINE);
    trackSelector.assertMappedTrackGroups(0, VIDEO_TRACK_GROUP, VIDEO_TRACK_GROUP);
    trackSelector.assertMappedTrackGroups(1, AUDIO_TRACK_GROUP);
  }

  /**
   * A {@link MappingTrackSelector} that stashes the {@link MappedTrackInfo} passed to {@link
   * #selectTracks(MappedTrackInfo, int[][][], int[])}.
   */
  private static final class FakeMappingTrackSelector extends MappingTrackSelector {

    private MappedTrackInfo lastMappedTrackInfo;

    @Override
    protected Pair<RendererConfiguration[], TrackSelection[]> selectTracks(
        MappedTrackInfo mappedTrackInfo,
        int[][][] rendererFormatSupports,
        int[] rendererMixedMimeTypeAdaptationSupports)
        throws ExoPlaybackException {
      int rendererCount = mappedTrackInfo.getRendererCount();
      lastMappedTrackInfo = mappedTrackInfo;
      return Pair.create(
          new RendererConfiguration[rendererCount], new TrackSelection[rendererCount]);
    }

    public void assertMappedTrackGroups(int rendererIndex, TrackGroup... expected) {
      TrackGroupArray rendererTrackGroupArray = lastMappedTrackInfo.getTrackGroups(rendererIndex);
      assertThat(rendererTrackGroupArray.length).isEqualTo(expected.length);
      for (int i = 0; i < expected.length; i++) {
        assertThat(rendererTrackGroupArray.get(i)).isEqualTo(expected[i]);
      }
    }

  }

  /**
   * A {@link RendererCapabilities} that advertises adaptive support for all tracks of a given type.
   */
  private static final class FakeRendererCapabilities implements RendererCapabilities {

    private final int trackType;

    public FakeRendererCapabilities(int trackType) {
      this.trackType = trackType;
    }

    @Override
    public int getTrackType() {
      return trackType;
    }

    @Override
    public int supportsFormat(Format format) throws ExoPlaybackException {
      return MimeTypes.getTrackType(format.sampleMimeType) == trackType
          ? (FORMAT_HANDLED | ADAPTIVE_SEAMLESS) : FORMAT_UNSUPPORTED_TYPE;
    }

    @Override
    public int supportsMixedMimeTypeAdaptation() throws ExoPlaybackException {
      return ADAPTIVE_SEAMLESS;
    }

  }

}