Even with a consistent standard library, you can't really be confident that you've properly refactored all usages of a class or function unless you have 100% te

Even with a consistent standard library, you can't really be confident that you've properly refactored all usages of a class or function unless you have 100% test coverage -- and even if you did, it would be difficult to automate the refactoring the way you could with a static language.