public void SetValue_AlreadyExists()
 {
     try
     {
         var sut = new FlagArgument(NAME, DESCRIPTION);
         sut.SetValue();
         sut.SetValue();
     }
     catch (Exception ex)
     {
         Assert.AreEqual("Argument was already provided", ex.Message);
         throw;
     }
 }
        public void SetValue()
        {
            var sut = new FlagArgument(NAME, DESCRIPTION);

            Assert.IsTrue(sut.Value == false);
            sut.SetValue();
            Assert.IsTrue(sut.Value == true);
        }