The phrase .contain.only or .only.contain takes a range, the elements of which are expected to be the only elements appearing in the range on the left hand side.
[3, 4].should.only.contain([4, 3]); [3, 4].should.only.contain([1, 2, 3, 4]); [3, 4].should.contain.only([4, 3]); [2, 3, 4].should.not.only.contain([4, 3]);
See Implementation
The phrase .contain.only or .only.contain takes a range, the elements of which are expected to be the only elements appearing in the range on the left hand side.