如何在JavaScript中使用Mocha和assert.throws测试参数的值？

Question

I want to see if a value that equals 'x' will cause my function to throw an exception. I have a unit test that checks if a block will throw an exception, but I want the exception to be thrown only if the argument = 'x', not if its just empty. How do I do this using assert?

Here's some code to illustrate what I mean:

// Some function to check if a color is not transparent.
function checkColor(color) {
  if (color == 'transparent') {
    throw new TypeError('cant have transparent colors!');
  } else {
    return color;
  }
}

Here's the assert:

assert.throws(checkColor, /cant have transparent colors!/);

Now, I know that assertion will fail because my function only throws the exception if the color == 'transparent'. Using Mocha and Assert, how do I test the assertion as I want it? I don't want to merely test if color !== undefined or is of some type. I specifically want to see if the exception is raised under the specific circumstance above - which is the only circumstance I want the exception to be raised (since having an empty color, is actually handled elsewhere).

Answer 1

assert.throw(function() { iThrowError(argument) }, Error)

现在只要确定参数= x;