public void TestCountMonths()
{
var dt1 = new DateTime(DateTime.Today.Year, 1, 14);
var dt2 = new DateTime(DateTime.Today.Year - 1, 12, 18);
var testResult = Rent.CountOfWholeCalendarMonthsBetween(dt1, dt2);
Assert.AreEqual(0, testResult);
testResult = Rent.CountOfWholeCalendarMonthsBetween(dt2, dt1);
Assert.AreEqual(0, testResult);
dt2 = new DateTime(DateTime.Today.Year - 1, 11, 5);
testResult = Rent.CountOfWholeCalendarMonthsBetween(dt1, dt2);
Assert.AreEqual(1, testResult);
dt2 = new DateTime(DateTime.Today.Year, 1, 1);
testResult = Rent.CountOfWholeCalendarMonthsBetween(dt1, dt2);
Assert.AreEqual(0, testResult);
dt1 = new DateTime(DateTime.Today.Year, 1, 1);
dt2 = new DateTime(DateTime.Today.Year + 1, 1, 1);
testResult = Rent.CountOfWholeCalendarMonthsBetween(dt1, dt2);
Assert.AreEqual(12, testResult);
dt1 = new DateTime(DateTime.Today.Year, 5, 5);
dt2 = new DateTime(DateTime.Today.Year, 11, 1);
testResult = Rent.CountOfWholeCalendarMonthsBetween(dt1, dt2);
Assert.AreEqual(5, testResult);
}