OpenCover Output with MSTest analyses same assembly twice

Question

I've been having a first go at using opencover for a current project, and have just got it working with my mstest project. I am having a problem though, in that the opencover output xml appears to trying to analyse the same assembly twice. Also worth note is that one of the analysis' shows 0% code coverage (which is wrong), whereas the other is more like 85% (which is correct).

My opencover command looks like:

"opencover.console.exe" -register:user -target:"C:\Program Files (x86)\Microsoft visual Studio 10.0\Common7\IDE\mstest.exe" -output:"C:\temp\coverage.xml" -targetargs:"/testcontainer:MyTestAssembly.dll" -filter:+[MyAssembly]MyNamespace.MyClassName

This is referring to a single assembly, and a single class in that assembly. However, the xml output has 2 module sectons, with the same hash. Interestingly, the first module has a FullName pointing at the assembly in my "\bin\Debug\MyAssembly.dll" folder, whereas the second one points at the output assembly in "C:\temp\TestResults...\Out\MyAssembly.dll".

Any ideas?

Matt

Answer 1

You need to use the -mergebyhash switch this is documented in the WIKI/USAGE

This is because mstest opens the assembly twice in different locations; once in its original location and then again in a test folder.

This option forces opencover to compare assemblies by a file hash and reuse the identifiers for sequence points for previously loaded assemblies. You may also need to use -targetdir, if it can't locate the PDBs, to point to the folder with them in but it usually does find them without extra help.