--- a/dom/media/gtest/TestVideoTrackEncoder.cpp
+++ b/dom/media/gtest/TestVideoTrackEncoder.cpp
@@ -347,9 +347,11 @@ TEST(VP8VideoTrackEncoder, EncodeComplet
   VideoSegment segment;
   encoder.NotifyQueuedTrackChanges(nullptr, 0, 0, TrackEventCommand::TRACK_EVENT_ENDED, segment);
 
   // Pull Encoded Data back from encoder. Since we have sent
   // EOS to encoder, encoder.GetEncodedTrack should return
   // NS_OK immidiately.
   EncodedFrameContainer container;
   EXPECT_TRUE(NS_SUCCEEDED(encoder.GetEncodedTrack(container)));
+
+  EXPECT_TRUE(encoder.IsEncodingComplete());
 }