public void EndOfMonth()
{
DateTime date;
DateTime endOfMonth;
// normal 30 day month
date = new DateTime(2018, 9, 15);
endOfMonth = date.EndOfMonth();
Assert.AreEqual(new DateTime(2018, 9, 15), date); // make sure that the original DateTime is not modified
Assert.AreEqual(new DateTime(2018, 9, 30), endOfMonth);
// normal 31 day month
date = new DateTime(2018, 12, 20);
endOfMonth = date.EndOfMonth();
Assert.AreEqual(new DateTime(2018, 12, 31), endOfMonth);
// february 28
date = new DateTime(2018, 2, 10);
endOfMonth = date.EndOfMonth();
Assert.AreEqual(new DateTime(2018, 2, 28), endOfMonth);
// february 29
date = new DateTime(2016, 2, 1);
endOfMonth = date.EndOfMonth();
Assert.AreEqual(new DateTime(2016, 2, 29), endOfMonth);
// already last day
date = new DateTime(1993, 1, 31);
endOfMonth = date.EndOfMonth();
Assert.AreEqual(new DateTime(1993, 1, 31), endOfMonth);
// current end of month
date = DateTime.Today.EndOfMonth();
endOfMonth = DateTimeUtility.EndOfMonth();
Assert.AreEqual(date, endOfMonth);
}