public void CreateWorkOrderValidationTests_ObjectNumber()
        {
            // error values
            _validator.ShouldHaveValidationErrorFor(x => x.ObjectNumber, null as string);
            _validator.ShouldHaveValidationErrorFor(x => x.ObjectNumber, string.Empty);

            // non-error values
            _validator.ShouldNotHaveValidationErrorFor(x => x.ObjectNumber, "B1");
            _validator.ShouldNotHaveValidationErrorFor(x => x.ObjectNumber, "B12");
            _validator.ShouldNotHaveValidationErrorFor(x => x.ObjectNumber, "B123");
        }