public void Validate_StrContainOpOnly_0Returned()
 {
     //arrage
     ExpressionValidator validator = new ExpressionValidator();
     //act
     bool result = validator.Check("+");
     //assert
     Assert.IsFalse(result);
 }
 public void Validate_1Op2_3Returned()
 {
     //arrage
     ExpressionValidator validator = new ExpressionValidator();
     //act
     bool result = validator.Check("1+2");
     //assert
     Assert.IsTrue(result);
 }