>>>>So, should I ask developer for PDB files or what should I do in order to debug the code using tests ?
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>>>Mock the dll....
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>>What exactly do you mean? Also, I do need the actual output of the Invoke1 call in order to proceed with the test.
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>I'm not going to write the code for you, but you can mock outside depencies for testing purposes. You eliminate classes outside of your control and feed the "mock" data to your test engine. I don't think you understand what "testing" really means. Here's the link: http://nmock.sourceforge.net/

The developer of that C++ library is having the same problem as me. He can only debug in Visual Studio 2010 and in 2012 he is getting the same error. So, for now I don't have another choice than to mock that part.