function expectHasBuffer(secondaryAudioVariant = false) {
    expect(mediaSourceEngine.initSegments).toEqual({
      audio: [false, true],
      video: [false, true],
      text: [],
    });
    expect(mediaSourceEngine.segments).toEqual({
      audio: [true, true, true, true],
      video: [true, true, true, true],
      text: [false, false, false, false],
    });
  }
Expect buffers have been added to MSE.
@param {boolean=} secondaryAudioVariant