function expectNoBuffer() {
    expect(mediaSourceEngine.initSegments).toEqual({
      audio: [false, false],
      video: [false, false],
      text: [],
    });
    expect(mediaSourceEngine.segments).toEqual({
      audio: [false, false, false, false],
      video: [false, false, false, false],
      text: [false, false, false, false],
    });
  }
Expect no buffer has been added to MSE.