public void AddLessThanValidationPredicate_WhenArgumentIsDouble()
{
// Arrange.
ValidatableArgument<double> argument = new ValidatableArgument<double>("argument", 3);
// Act.
argument.IsLessThan(5);
// Assert.
Assert.AreEqual(1, argument.ValidationPredicates.Count());
Assert.IsInstanceOfType(argument.ValidationPredicates.First(), typeof(LessThanValidationPredicate<double>));
}