test('pass verifier, with passing rule, has no errors', () => {
    const verifier = makeVerifierWithPassingRule();
    const errors = verifier.verify('any input');
    expect(errors.length).toBe(0);
});

test('pass verifier, with passing and failing rule, ' + 'has one error', () => {
    const verifier = makeVerifierWithFailedRule('fake reason');
    verifier.addRule(passingRule);
    const errors = verifier.verify('any input');
    expect(errors.length).toBe(1);
});

test('pass verifier, with passing and failing rule, ' + 
     'error text belongs to failed rule', () => {
    const verifier = makeVerifierWithFailedRule('fake reason');
    verifier.addRule(passingRule);
    const errors = verifier.verify('any input');
    expect(errors[0]).toContain('fake reason');
});