Yes, I (as well as the commenter above, I assume) just doubt that the sheer number of tests will do this in a useful manner. If you have a giant bunch of code

Yes, I (as well as the commenter above, I assume) just doubt that the sheer number of tests will do this in a useful manner. If you have a giant bunch of code that has been written without testability in mind, adding tons of tests mostly just locks down the interfaces of every single segment of code, making refactoring really hard to a point where the tests are useless because they have to be rewritten as well anyways. Good test are written for good code that is written with testability in mind. In that case, only the relevant interfaces are proplery tested and not every little internal thing, which allows for proper refactoring and expansion without fiddling with the tests. This however also yields a lot fewer tests, which is why I doubt this large number of tests can be high quality and/or beneficial.