AssertWith doesn't behave properly when calling a function with the same arguments

[xp500]

Asserting that a function has been called with a given parameter fails if that function was called with that parameter with an arity greater than one.

For example, the following assertions fail if the function sum is called with sum(1, 1).

expect(sum).to.have.been.called.with(1) (1)
expect(sum).to.have.been.called.with(1, 1) (2)

The reason is that the function assertWith counts all the occurrences of the parameters for each argument and then expects it to be equal to the length of the arguments.

Assertion (1) will fail because 1 appears twice in the arguments list, but the length of the with arguments is 1.

Assertion (2) will also fail because 1 appears twice in the arguments list, so for every with argument it is counted twice, so it's been found "4" times.