Unit test generator

Just an idea: what if we had the software that would automatically generate unit tests for all success scenarios? It would work like this:
1. Attach to the running process as a debugger
2. The user would use the application to test all success scenarios
3. The generator program would record all the method invocations with all the parameters.
4. After the application that is being debugged exits the generator program would use the information about methods invocation and generate NUnit tests.