Code is behaving differently in Release vs Debug Mode

Question

We have some unit tests that fail when run in Release mode vs debug mode. If I attach a debugger in release mode the tests pass. There is way too much code to publish here s

Answer 1

Questions you should ask yourself -

1. Is my code threaded? Timing differences will affect output
2. Is someone calling Debug.Assert() with an expression that side effects?
3. What objects implement IDisposable() and do some do so in such a way that changes state?
4. Are you P/Invoking into unmanaged code?

Number 3 is a very likely bad-boy in this case. Garbage collection may be very different in debug and release and you may find that when an object is garbage collected is affecting the outcome of a later unit test.

And FYI, if you're using NUnit and TestDriven.NET - the two run tests in different orders.