public void Mix()
    {
        var vm = new UppercaseModel {
            Password = "******"
        };

        var validations = vm.Validate(vm.Password, _password);

        validations.Print(_output);

        Assert.Empty(validations);
    }
    public void Lowercase()
    {
        var vm = new UppercaseModel {
            Password = "******"
        };

        var validations = vm.Validate(vm.Password, _password);

        validations.Print(_output);

        Assert.Collection(validations, v =>
                          v.ErrorMessage = "Uppercase is required");
    }