### Question:
Stopwatch { public Event stop(String eventName) { return stopEvent(eventName); }  void start(String eventName); Event stop(String eventName); void lap(String eventName);  }### Answer:
@Test(expected = IllegalArgumentException.class) public void shouldThrowExceptionWhenStopButNotStarted() { Stopwatch stopwatch = new Stopwatch(); stopwatch.stop("e"); }