问抛出mocha异常可以使测试通过，而不应该这样做。

EN

  // this would pass
  it('adsf', async () => {
    assert.equal(1,1)
    var foo = undefined;
    foo.hi(); // throw exception
    assert.equal(1,2) // assert not called
  });

  // this would fail, but not say why
  it('adsf', async () => {
    try {
      assert.equal(1,1)
      // var foo = undefined;
      // foo.hi();
      assert.equal(1,2)
    } catch (err) {
      assert.fail(err) // if fail, such as the 1,2 case above, the line number of the error is not shown
    }
  });