Writing a plugin/module for testing, any feedback required.
It might be able to hook into the debugger api, which triggers breakpoints if set anywhere. Furthermore you can retrieve a lot of runtime information by hooking into the Core.registerProfiler
I would appreciate a plugin functionality for the Modeler as well, but it is not available.
There is no option to do code coverage in Mendix, because the microflows are interpreted by the Mendix runtime, which has no API do to code coverage. It should be nice if Mendix itself should supply this.