Which means it's often difficult. The traits "Has a comprehensive test suite" and "is spaghetti code" are often rarely seen together. A poor code base has becom

Which means it's often difficult. The traits "Has a comprehensive test suite" and "is spaghetti code" are often rarely seen together. A poor code base has become poor because it's not refactored and cleaned up all the time - and that's often because their is no tests to help with that. And if there is no test suite, there is often very few ways to add a test suite. Poor code has very few points where you can attach a test. If the code contains file databases or structured input of some sort (a web page) you can add some very high level end to end tests. But not all code has easily verifiable endpoints like that. Perhaps my bad experiences comes from "hard to test" domains (Sound, drawing, ...) code, and not "given this input this is written to the database and this is written to screen".