Just writing about refactoring environment which can be best when you are doing refactoring in your code base. Refactoring can be done at any time of your code. When you are refactoring code you can see follow things is a benefit for you.

1. Have some good tests for which code you are going to refactor.
2. Let’s pair when you start refactoring. Having a pair while doing refactoring is a great idea.
3. Code must be under version control. GIT/SVN