Avoid adding spy to list in DataSourceContractTests

After the fix in mockito/mockito#2331, the calls to
equals on the fake transfer listener (due to its use in a list of listeners)
are treated as interactions with it, meaning that the current verification of
'no more interactions' will fail.

This change makes the transfer listener used for testing count bytes then
delegate to another (mock) transfer listener that's passed in to avoid the
problem.

PiperOrigin-RevId: 391949619

testutils/src/main/java/com/google/android/exoplayer2/testutil/DataSourceContractTest.java

@@ -24,7 +24,6 @@
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
@@ -391,8 +390,10 @@ public void transferListenerCallbacks() throws Exception {
     for (int i = 0; i < resources.size(); i++) {
       additionalFailureInfo.setInfo(getFailureLabel(resources, i));
       DataSource dataSource = createDataSource();
-      FakeTransferListener listener = spy(new FakeTransferListener());
-      dataSource.addTransferListener(listener);
+      TransferListener listener = mock(TransferListener.class);
+      ByteCountingTransferListener byteCountingTransferListener =
+          new ByteCountingTransferListener(listener);
+      dataSource.addTransferListener(byteCountingTransferListener);
       InOrder inOrder = Mockito.inOrder(listener);
       @Nullable DataSource callbackSource = getTransferListenerDataSource();
       if (callbackSource == null) {
@@ -430,7 +431,8 @@ public void transferListenerCallbacks() throws Exception {
         }
         // Verify sufficient onBytesTransferred() callbacks have been triggered before closing the
         // DataSource.
-        assertThat(listener.bytesTransferred).isAtLeast(resource.getExpectedBytes().length);
+        assertThat(byteCountingTransferListener.bytesTransferred)
+            .isAtLeast(resource.getExpectedBytes().length);
 
       } finally {
         dataSource.close();
@@ -615,23 +617,37 @@ public TestResource build() {
     }
   }
 
-  /** A {@link TransferListener} that only keeps track of the transferred bytes. */
-  public static class FakeTransferListener implements TransferListener {
+  /** A {@link TransferListener} that keeps track of the transferred bytes. */
+  private static final class ByteCountingTransferListener implements TransferListener {
+
+    private final TransferListener transferListener;
+
     private int bytesTransferred;
 
+    public ByteCountingTransferListener(TransferListener transferListener) {
+      this.transferListener = transferListener;
+    }
+
     @Override
-    public void onTransferInitializing(DataSource source, DataSpec dataSpec, boolean isNetwork) {}
+    public void onTransferInitializing(DataSource source, DataSpec dataSpec, boolean isNetwork) {
+      transferListener.onTransferInitializing(source, dataSpec, isNetwork);
+    }
 
     @Override
-    public void onTransferStart(DataSource source, DataSpec dataSpec, boolean isNetwork) {}
+    public void onTransferStart(DataSource source, DataSpec dataSpec, boolean isNetwork) {
+      transferListener.onTransferStart(source, dataSpec, isNetwork);
+    }
 
     @Override
     public void onBytesTransferred(
         DataSource source, DataSpec dataSpec, boolean isNetwork, int bytesTransferred) {
+      transferListener.onBytesTransferred(source, dataSpec, isNetwork, bytesTransferred);
       this.bytesTransferred += bytesTransferred;
     }
 
     @Override
-    public void onTransferEnd(DataSource source, DataSpec dataSpec, boolean isNetwork) {}
+    public void onTransferEnd(DataSource source, DataSpec dataSpec, boolean isNetwork) {
+      transferListener.onTransferEnd(source, dataSpec, isNetwork);
+    }
   }
 }