I'm still not sure I'm understanding this.  This statement:

    !isFinite(videoPlayer.currentTime) || and videoPlayer.currentTime <= 0

ensures that the video has started playing.  But what if `pause` is called before these lines execute:

    expect(videoPlayer.startTime).toBe(START_TIME);
    expect(videoPlayer.endTime).toBe(END_TIME);

Based on the `expect` statements in the `run` function below, wouldn't these fail?  (Because the `startTime` would be 0 and the `endTime` would be null)