Asserts that a Set is empty.

expect(new Set(), 'to be empty');

In the case of a failing expectation you get the following output:

expect(new Set([1, 2, 3]), 'to be empty');

expected new Set([ 1, 2, 3 ]) to be empty

The assertion can be negated using the not flag:

expect(new Set([1, 2, 3]), 'not to be empty');

And with a failing expectation:

expect(new Set(), 'not to be empty');

expected new Set([]) not to be empty