As Kent C. Dodds says I think it's better to get hands on the actual problem before the test. It's what you need after all.
When the feature seems to be working as you wanted, then start writing tests and fix errors that occurs. Next step is to refactor the code and clean it up, while the tests still works. You can call my approach STR for Sketch, Test, Refactoring - or some might say Sketch Test Driven.. STD :D
Focus should not be on the procedure, but on the problem. (Test and refactor are focus on future problems in this case, or to avoid them of course.)