I worked deeply with both static and dynamic languages as well. I do feel that it's easier to refactor in scala than ruby, especially in large projects. In rub

I worked deeply with both static and dynamic languages as well. I do feel that it's easier to refactor in scala than ruby, especially in large projects. In ruby, you have to have close to 100% test coverage because if you don't you can't have any confidence when you refactor. For example, in ruby project, even a simple delegation call needs to be tested, otherwise you may break it without knowing it when you rename the method delegated to. You don't need to write such test in a Scala project because there is no business logic in a simple delegation and the compiler will check the rename for you, actually the IDE will do the rename refactor perfectly for you. In general, some of the unit tests devs wrote in Ruby projects are not to test against business logic but to test type matching. For type related refactoring, they actually have to refactor both the code and unit tests. The dilemma here is that if you are changing your unit tests, how confident you are that they are still covering your refactor?