public void ReturnTrueAndMatchMessage_WhenArgumentIsNull()
{
// Arrange.
int? value = null;
// Act.
IValidationPredicateResult result = NullableNullValidationPredicate<int>.Instance.Match(value);
// Assert.
Assert.IsTrue(result.IsMatch);
Assert.AreEqual("The argument is null.", result.Message);
}
}