c# - DateTime.AddDays what value to pass to generate an exception -

c# - DateTime.AddDays what value to pass to generate an exception -

i have little utility class generate hash code input data. class & algorithm not important question looks below:

public static class hashcodehelper { /// <summary> /// homecoming hash code added link in download data. /// </summary> /// <param name="basedatetime">today's date</param> /// <param name="rrid">profile id</param> /// <param name="downloadcode">download code used hash code generation.</param> /// <returns>final result string in format "20140715385"</returns> public static string generatehashcodeforexportlink(datetime basedatetime, int rrid, string downloadcode) { var todaydate = basedatetime; int expireindays; if (!int.tryparse(configurationmanager.appsettings["exportlinkexpireindays"], out expireindays)) expireindays = 30; // if not specified in web.config file utilize default value var expirydate = todaydate.adddays(expireindays); var currentday = todaydate.day; var expirymonth = expirydate.month; char nthchar = convert.tochar(downloadcode.substring(expirymonth - 1, 1)); var asciivalue = (int)nthchar; var mod = (rrid % currentday); var computedhash = (asciivalue * expirymonth) + currentday + mod; var fullhashcode = todaydate.tostring("yyyymmdd") + computedhash; homecoming fullhashcode; } }

i writing unit test cases class , realized adddays() can throw argumentoutofrangeexception, below line:

var expirydate = todaydate.adddays(expireindays);

so should write test , did write below test case:

[testmethod] public void generatehashcodeforexportlink_incorrectdate_throw() { seek { hashcodehelper.generatehashcodeforexportlink(new datetime(2015, 1, 31), 501073, "001-345-673042"); assert.fail("exception not thrown"); } grab (argumentoutofrangeexception) { } grab (exception) { assert.fail("incorrect exception thrown"); } }

the problem is, not know pass cause adddays() method throw exception? tried passing random dates e.g. 1-1-1800, 30-jan-2015, etc.

i looked @ adddays() method implementation not create out. idea?

if pass in int.maxvalue, should end value outside representable range datetime, whatever original datetime is.

sample code, tested on csharppad.com:

datetime.minvalue.adddays(int.maxvalue);

using assert.fail in finally block error though... always called. it's not clear test framework is, i'd expect like:

assert.throws<argumentoutofrangeexception>(() => /* code here */);

c# unit-testing