Add daily email for 2024-09-01

You need tests to refactor safely

source/_daily_emails/2024-09-01.md

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+---
+title: You need tests to refactor safely
+date: 2024-09-01
+permalink: daily/2024/09/01/you-need-tests-to-refactor-safely
+tags:
+    - software-development
+    - refactoring
+    - automated-testing
+    - test-driven-development
+cta: call
+snippet: |
+    When refactoring, you should have automated tests to ensure it's done safely.
+---
+
+[Once you have working code][0], you can refactor it to make it better.
+
+You can rename variables, extract new functions or classes, ensure the code is styled and formatted correctly - anything to make the code easier to read, understand or maintain.
+
+But, the key thing is the code still needs to work.
+
+You don't want to break working code and introduce a regression, even if it is messy or difficult to read.
+
+The best way I know to approach this is by having automated tests covering this code, and ensure they are working and passing before starting to refactor.
+
+Then you can run the tests again and ensure they still pass.
+
+If they pass, the code still works and the refactoring was successful.
+
+If not, the code is broken and you need to revert the changes and start again.
+
+[0]: {{site.url}}/daily/2024/08/31/make-it-work-then-make-it-good