In VS2005 running Unit Tests with Code Coverage enabled and having the Assembly signed all unit tests fail. You may see then an error message “Strong name validation failed“. The reason is simple.

The instrumentation for code coverage modifies binaries and so it removes the strong name signature. In order the binary to be reused, it needs to be re-signed after instrumentation. This may be done via run configuration editor (Test | Edit Test Run Configurations…), ‘Code Coverage‘ tab, “Re-signing key file” edit field. You can specify binaries, which need re-signing and what key file to be used for that process.