Mono MCS Errors. Errors in the Mono C# compiler use the same codes as the Microsoft C# compiler, the listing of the errors on it lives in: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cscomp/html/vctbsCompilerErrorsSC0001ThroughSC9999.asp * Format Error tests are stored in files with the format: csXXXX.cs for the first error. csXXXX-2.cs for the second way to trigger the error. csXXXX-n.cs for subsequent ways of triggering the error. The file should start with two inline commented lines. The first one contains a little description of the error, the second line declares the line where the error occurs. You should not copy Microsoft's examples or documentation text. You will need to write your own. For example: // cs0057.cs: Inconsistent accessibility. Parameter type is less accessible than operator. // Line: 10 There should not be more than one error per tests. Each test should only contain one error. Then you have to add the file to the CVS and commit it. The next thing is to write a short text file with a little description of what the error is and what it's necessary to be done to solve it.