> Don’t get me wrong I’m not saying to scrap all your test suites and try to encode all your constraints using the type system instead. Not at all I still firml

> Don’t get me wrong I’m not saying to scrap all your test suites and try to encode all your constraints using the type system instead. Not at all I still firmly believe that tests are useful but in some cases you can leverage the type system to avoid mistakes. You should still write unit tests. You should also write integration/functional tests that might have caught this error when you tested the code that calls the function in question. The only scenario I can see the argument swapping bug not being caught is when all of the ID arguments equal the same value.