I do Integrunit tests Rules: Cover a whole functionality, not just a single file/class/function. Can't use I/O except reading in-codebase test-data files. Mu

I do Integrunit tests Rules: Cover a whole functionality, not just a single file/class/function. Can't use I/O except reading in-codebase test-data files. Must be fast. Mock only external technical dependencies, not own code.