beforeEach(() => {
            fakeRule = () => ({  passed: false, reason: 'fake reason'  });
            verifier.addRule(fakeRule);
            errors = verifier.verify('any value');
        });

        it('has an error message based on the rule.reason', () => {
            expect(errors[0]).toContain('fake reason');
        });

        it('has exactly one error', () => {
            expect(errors.length).toBe(1);
        });
    });

    describe('with a passing rule', () => {
        let fakeRule, errors;

        beforeEach(() => {
            fakeRule = () => ({  passed: true, reason: ''  });
            verifier.addRule(fakeRule);
            errors = verifier.verify('any value');
        });