Add shouldContainOnly

[klitoskyriacou]

It would be useful to have an assertion that is exactly equivalent to AssertJ's assertThat(list).containsOnly(these,elements,in,any,number,and,any,order,and,nothing,else).

For example:

listOf(1, 1, 1).shouldContainOnly(1)   // expected to pass
listOf(1, 1, 2, 2).shouldContainOnly(1, 2)  // expected to pass
listOf(1, 1, 2).shouldContainOnly(1)   // expected to fail because it shouldn't contain 2
listOf(1, 1, 2).shouldContainOnly(1, 2, 3)  // expected to fail because it doesn't contain 3

[LeoColman]

I think this is a tough one.

listOf(1, 1, 2, 2) shouldContainOnly listOf(1, 2)

is pretty ambigous to me what should actually be the result here just from the name

[klitoskyriacou]

It's not ambiguous, because you wouldn't call it like that. shouldContainOnly should take a vararg, not a list. Just as shouldContainExactly does.

If you want to use infix functions, it's list should containOnly(1, 2).

[p1729]

@LeoColman I would like to contribute to this.

[LeoColman]

Go for it! I'll assign it to you