Refactoring

A practical example of refactoring a part of the MoJ video hearings service website questionnaire journey.

Transcript

1. Refactoring A practical example Photo by Yung Chang on Unsplash
2. Refactoring ➔ Not scheduled It’s cleaning up before or better yet, after we do something. ➔ Not rewriting We’re moving code, not changing functionality ➔ Iterative Run test. Tinker (move code, rename). Run test. Repeat. ➔ Requires test When you have tests you can refactor without fear.
3. SuitabilityChoiceTextboxComponentBase
4. Initial solution: inheritance
5. PROBLEM: New base class. But we want same functionality.
6. uh-oh
7. So we refactor. The first solution worked. It was fine. Next time? Probably takes longer, more tests more bugs and harder to do. Let’s clean up! Photo by Emma Matthews on Unsplash
8. We have one sub-class per textbox choice page, all have ~8 tests testing the exact same functionality. Step 1 Find a problem. Here be Duplication.
9. Break out functionality. Make it reusable. Test it. Step 2 Duplicate some Break out and generalise Forward/wrap functionality, tests ✓
10. Step 3 Decouple base class. No functionality change, tests ✓
11. Remove superfluous code Step 4 Remove duplicate tests. Run tests, ✓, coverage 100% PR & run acceptance tests, page still works.
12. After proving it works. Rinse and repeat. Step 5 Bypass base component in other components. Run tests ✓ Check usages. None. Delete. Tests still ✓
13. Can now remove all duplicated tests. Coverage still 100% because they were testing the same thing.
14. Result? A little more code in components, code that actually belonged in there. Far fewer classes. No test duplication. Functionality tested once = less maintenance. Decoupling. Same form, different journeys.
15. Summary 1. We never know how to do it the first time, no point trying 2. We make it work instead 3. Then we make it maintainable 4. Then we repeat
16. Disclaimers and observations • Process a little different from actual steps. • Many more iterations than described. • I tried things, redid many times • I did PR early ◦ Runs acceptance tests ◦ Shows complexity/flow ◦ Smaller increments
17. FIN.