Simplest way to calculate leap year

During my previous talk on C# programming, I have asked 'How to calculate a leap and what is the easiest way to make it testable.

There're numerous answers from the audience. I was surprised that everyone is doing all the old way. In following code snippet, I found this is the easiest and shortest one way:

public static bool IsLeapYear(int year)
       {
           return (year%4==0 || year%400==0);
       }

Above, method is just asking to supply an integer having year and it will return true/false quoting whether the year is a leap year. The idea behind this is the common i.e. a leap year which comes at every fourth year.

[TestFixture]
    [Category("The LeapYear")]
    public class LeapYearTest
    {
        [Test]
        public void CanTestForLeapYear()
        {
            Assert.That(true, Is.EqualTo(LeapYear.IsLeapYear(1996)));
        }

        [Test]
        [TestCase(false, 2013)]
        [TestCase(false, 2001)]
        [TestCase(true, 1996)]
        [TestCase(true, 1992)]
        public void CanTestForLeapYears(bool expectedResult, int year)
        {
            Assert.That(expectedResult, Is.EqualTo(LeapYear.IsLeapYear(year)));
        }
    }

Above is showing Test, I did not make any special validation as this is just to say the shortest/easiest method to calculate leap year.

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