Unit testing TypeInitializationException error

Question

I am working on a unit testing for a function in a form call Tester.cs, below is the error:

Error   7/31/2012 10:43:11 PM   One of the background threads threw exception: 
System.TypeInitializationException: The type initializer for 'Tester.Tester' threw an exception. ---> System.ArgumentNullException: Value cannot be null.
Parameter name: String
   at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   at System.Int32.Parse(String s)
   at Tester.Tester..cctor() in E:\Incubator\Tester\Tester\Tester.cs:line 35
   --- End of inner exception stack trace ---
   at Tester.Tester.Dispose(Boolean disposing)
   at System.ComponentModel.Component.Finalize()    MY-PC

On line 35 is a code, which basically retrieve value from configuration file and convert it to integer:

private static int _part = int.Parse(ConfigurationManager.AppSettings["Part"]);

What is the error? Thank you.

Answer 1

The likelyhood is that ConfigurationManager.AppSettings["Part"] is returning null. Hense the parse exception.

Does your unit test project have the app setting defined in its configuration?

Answer 2

You should copy your app.config (or web.config) file into test project. Otherwise test project can't find it. Remember config is related to host process, not to the dll itself.