I am currently working on a project with a pluggable application (load plugins at runtime and execute them) that loads assemblies at runtime, using the Assembly.LoadFile() method. I wanted to test it using NUnit (feel free to read our 3 Ways to Run NUnit from Visual Studio post). Although, the code was functioning very well it always failed during the NUnit tests, always! It took me several days to understand what went wrong and I want to share you with my findings.