Rubberduck
Every programmer needs a rubberduck. COM add-in for the VBA & VB6 IDE
.... Navigate a Classic-VB project like never before, quickly locating identifier references, interface implementations, and anything else that has a name. Add a full folder structure for organizing your modules. Write code that runs your code and verifies its output is as expected, given controlled inputs. Organize tests into categories, run them directly in the VBIDE, and view results in a dedicated explorer toolwindow.