public void GetHashCode_gets_hash_code_from_every_rule(IEqualityRule <string> rule1,
                                                               IEqualityRule <string> rule2,
                                                               string str)
        {
            var sut = new MultipleEqualityRuleRunner <string>(new [] { rule1, rule2 });

            sut.GetHashCode(str);

            Mock.Get(rule1).Verify(x => x.GetHashCode(str), Times.Once);
            Mock.Get(rule2).Verify(x => x.GetHashCode(str), Times.Once);
        }