Add assertion helper to verify MediaSource/TrackGroups/TrackSelection/StreamKey cycle.

This is useful to write integration tests for MediaSources which check that the
stream keys returned by getStreamKeys are compatible with the respective manifest
parser.

PiperOrigin-RevId: 225542606

testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/MediaPeriodAsserts.java

@@ -0,0 +1,178 @@
+/*
+ * Copyright (C) 2018 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.testutil;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.support.annotation.Nullable;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.offline.FilterableManifest;
+import com.google.android.exoplayer2.offline.StreamKey;
+import com.google.android.exoplayer2.source.MediaPeriod;
+import com.google.android.exoplayer2.source.MediaPeriod.Callback;
+import com.google.android.exoplayer2.source.TrackGroup;
+import com.google.android.exoplayer2.source.TrackGroupArray;
+import com.google.android.exoplayer2.trackselection.BaseTrackSelection;
+import com.google.android.exoplayer2.trackselection.TrackSelection;
+import com.google.android.exoplayer2.util.ConditionVariable;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
+
+/** Assertion methods for {@link MediaPeriod}. */
+public final class MediaPeriodAsserts {
+
+  /**
+   * Interface to create media periods for testing based on a {@link FilterableManifest}.
+   *
+   * @param <T> The type of {@link FilterableManifest}.
+   */
+  public interface FilterableManifestMediaPeriodFactory<T extends FilterableManifest<T>> {
+
+    /** Returns media period based on the provided filterable manifest. */
+    MediaPeriod createMediaPeriod(T manifest);
+  }
+
+  private MediaPeriodAsserts() {}
+
+  /**
+   * Asserts that the values returns by {@link MediaPeriod#getStreamKeys(TrackSelection)} are
+   * compatible with a {@link FilterableManifest} using these stream keys.
+   *
+   * @param mediaPeriodFactory A factory to create a {@link MediaPeriod} based on a manifest.
+   * @param manifest The manifest which is to be tested.
+   */
+  public static <T extends FilterableManifest<T>>
+      void assertGetStreamKeysAndManifestFilterIntegration(
+          FilterableManifestMediaPeriodFactory<T> mediaPeriodFactory, T manifest) {
+    MediaPeriod mediaPeriod = mediaPeriodFactory.createMediaPeriod(manifest);
+    TrackGroupArray trackGroupArray = getTrackGroups(mediaPeriod);
+
+    for (int i = 0; i < trackGroupArray.length; i++) {
+      TrackGroup trackGroup = trackGroupArray.get(i);
+
+      // For each track group, create various test selections.
+      List<TrackSelection> testSelections = new ArrayList<>();
+      for (int j = 0; j < trackGroup.length; j++) {
+        testSelections.add(new TestTrackSelection(trackGroup, j));
+      }
+      if (trackGroup.length > 1) {
+        testSelections.add(new TestTrackSelection(trackGroup, 0, 1));
+      }
+      if (trackGroup.length > 2) {
+        int[] allTracks = new int[trackGroup.length];
+        for (int j = 0; j < trackGroup.length; j++) {
+          allTracks[j] = j;
+        }
+        testSelections.add(new TestTrackSelection(trackGroup, allTracks));
+      }
+
+      // Get stream keys for each selection and check that the resulting filtered manifest includes
+      // at least the same subset of tracks.
+      for (TrackSelection testSelection : testSelections) {
+        List<StreamKey> streamKeys = mediaPeriod.getStreamKeys(testSelection);
+        T filteredManifest = manifest.copy(streamKeys);
+        MediaPeriod filteredMediaPeriod = mediaPeriodFactory.createMediaPeriod(filteredManifest);
+        TrackGroupArray filteredTrackGroupArray = getTrackGroups(filteredMediaPeriod);
+        Format[] expectedFormats = new Format[testSelection.length()];
+        for (int k = 0; k < testSelection.length(); k++) {
+          expectedFormats[k] = testSelection.getFormat(k);
+        }
+        assertOneTrackGroupContainsFormats(filteredTrackGroupArray, expectedFormats);
+      }
+    }
+  }
+
+  private static void assertOneTrackGroupContainsFormats(
+      TrackGroupArray trackGroupArray, Format[] formats) {
+    boolean foundSubset = false;
+    for (int i = 0; i < trackGroupArray.length; i++) {
+      if (containsFormats(trackGroupArray.get(i), formats)) {
+        foundSubset = true;
+        break;
+      }
+    }
+    assertThat(foundSubset).isTrue();
+  }
+
+  private static boolean containsFormats(TrackGroup trackGroup, Format[] formats) {
+    HashSet<Format> allFormats = new HashSet<>();
+    for (int i = 0; i < trackGroup.length; i++) {
+      allFormats.add(trackGroup.getFormat(i));
+    }
+    for (int i = 0; i < formats.length; i++) {
+      if (!allFormats.remove(formats[i])) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  private static TrackGroupArray getTrackGroups(MediaPeriod mediaPeriod) {
+    AtomicReference<TrackGroupArray> trackGroupArray = new AtomicReference<>(null);
+    DummyMainThread dummyMainThread = new DummyMainThread();
+    dummyMainThread.runOnMainThread(
+        () -> {
+          ConditionVariable preparedCondition = new ConditionVariable();
+          mediaPeriod.prepare(
+              new Callback() {
+                @Override
+                public void onPrepared(MediaPeriod mediaPeriod) {
+                  preparedCondition.open();
+                }
+
+                @Override
+                public void onContinueLoadingRequested(MediaPeriod source) {
+                  // Ignore.
+                }
+              },
+              /* positionUs= */ 0);
+          try {
+            preparedCondition.block();
+          } catch (InterruptedException e) {
+            // Ignore.
+          }
+          trackGroupArray.set(mediaPeriod.getTrackGroups());
+        });
+    dummyMainThread.release();
+    return trackGroupArray.get();
+  }
+
+  private static final class TestTrackSelection extends BaseTrackSelection {
+
+    public TestTrackSelection(TrackGroup trackGroup, int... tracks) {
+      super(trackGroup, tracks);
+    }
+
+    @Override
+    public int getSelectedIndex() {
+      return 0;
+    }
+
+    @Override
+    public int getSelectionReason() {
+      return C.SELECTION_REASON_UNKNOWN;
+    }
+
+    @Nullable
+    @Override
+    public Object getSelectionData() {
+      return null;
+    }
+  }
+}