support .withArgs() on expect(fn)

expect.js has a feature to pass arguments to a function using the following syntax

expect(fn).withArgs(some, args).to.throw();

Right now I’m having to write the following

expect(() => fn(some, args)).to.throw();

[keithamus]

fn.should.throw.with.args(some, args);

Would probably fit more with the rest of the code. Having args as the assertion actually makes for some interesting developments:

addNumbers.should
  .throw.with.args(1, 'a')
  .and.args('a', 2)
  .but.not.throw.with.args(1, 2)

It becomes challenging though - because we can’t assert on the error that is being thrown in a sensible way:

addNumbers.should.throw/* a typeerror, but I can't assert this */.with.args(1, 'a')

Whereas if the args was in the chain, then we can:

addNumbers.should.with.args(1, 'a').throw(TypeError)

[lucasfcosta]

@blockloop IMO that is not a viable solution because it adds another property to the Object.prototype. I think that having should is already enough. If we did that it would be like a new Assertion interface.