.offset.setValueAtTime(0.5, testTime);
            refSrc.offset.linearRampToValueAtTime(1, rampEnd);

            src.start();
            refSrc.start();

            context.startRendering()
                .then(audio => {
                  const actual = audio.getChannelData(0);
                  const expected = audio.getChannelData(1);

                  // Just verify that the actual output matches the expected
                  // starting a little bit before testTime.
                  let testFra