Refactoring tests could be painful a lot. But it could also give you a lot of fun too. During refactoring unit tests, I’ve found a log of issues to be resolved. Also, it gives me more knowledge about how the project works.
Refactoring tests could be harder than refactoring rest of code because it could affect not only tests.
Since there are no tests for tests, there is only one way to understand if refactoring didn’t lead to less test coverage. It’s required to measure testsc overage before and after refactoring. New tests coverage should be equal to or more than the old one.
It’s important to keep code quality for tests too. Tests are the same code as any other. That means, that you have to follow the same patterns and practices: code reviews, KISS, DRY, etc. It’s extremely dangerous to not do code review just because ‘it’s unit tests’.