fix broken 'ok' assertions in tests

[Lysander6]

should.js' ok assertions must be called to work properly

this doesn't raise error:

describe.only('should.be.ok', function() {
    it('passes, but should not', function() {
        var x = false;
        x.should.be.ok;
    });
});

fails as it should:

describe.only('should.be.ok', function() {
    it('fails as it should', function() {
        var x = false;
        x.should.be.ok();
    });
});

[Lysander6]

same goes for other assertions like .should.be.true, .should.be.a.Function, etc. which I fixed as well

[LinusU]

Nice catch 👍

[dougwilson]

Ah, yea, probably a behavior change in some upgrade of should.