The Slim server is started and stopped by FitNesse when we run a test, so there is no chance to attach to it and set breakpoints. To help debug our fixture code, we can use the GUI Slim server. This requires a change to the TEST_RUNNER definition.

!define TEST_RUNNER {c:\apps\fitSharp\RunnerW.exe}

When a Slim test is executed, this test runner opens a window and waits for us to press the Go button. We can attach our debugger to the test runner and set breakpoints in our fixture code. Pressing Go starts the test and pressing it again returns control to FitNesse.

We can also use this test runner to troubleshoot problems when a Slim test appears to hang. Any unhandled exceptions are caught and displayed in the test runner window.

This does not work if we have SLIM_PORT defined as 1 - this is the default and so another port must be defined.