Proposed Solution Day 23

advent-of-craft · Dec 24, 2023 · 9bee113 · 9bee113
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@@ -95,6 +95,7 @@ A solution proposal will be published here every day during the `Advent Of Craft
 - [Day 20: No more exceptions in our domain.](solution/day20/docs/step-by-step.md)
 - [Day 21: Refactor the tests and production code to Output-Based tests.](solution/day21/docs/step-by-step.md)
 - [Day 22: Design a diamond program using T.D.D and Property-Based Testing.](solution/day22/docs/step-by-step.md)
+- [Day 23: Refactor the code after putting it under test.](solution/day23/docs/step-by-step.md)
 
 ## Contributors
 

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+# Day 23: Refactor the legacy code after putting it under test.
+Refactor the `TripService` class to ensure Clean Code / SOLID principles
+
+Legacy code golden rules :
+`You cannot change any existing code if not covered by tests.`
+
+The only exception is if we need to change the code to add unit tests, but in this case, just automated refactorings (via IDE) are allowed.
+
+## Step by Step
+
+We use different steps that are all described separately (step-by-step md files):
+
+1. Cover the production code
+2. Improve confidence in our tests
+3. Refactor the production code
+4. Other refactorings
+
+## What did we use / learn ?
+- `Seams`
+- `Automated refactoring` via our IDE
+  - Extract Method
+  - Change Signature
+  - Rename
+- `Mutation Testing`
+- Use `Higher Order Functions` to avoid duplication
+- Use `code coverage` as a driver
+- `Test Data Builder`
+- `Feature Envy`
+- `Sprout Class`
+- `TDD`
+
+>**Tip of the day1: Start testing from shortest to deepest branch.**
+
+>**Tip of the day2: Start refactoring from deepest to shortest branch.**
+
+### Share your experience
+
+How does your code look like?
+
+Please let everyone know in the discord.
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+# Day 23: Refactor the legacy code after putting it under test.
+Refactor the `TripService` class to ensure Clean Code / SOLID principles
+
+Legacy code golden rules :
+`You cannot change any existing code if not covered by tests.`
+
+The only exception is if we need to change the code to add unit tests, but in this case, just automated refactorings (via IDE) are allowed.
+
+## Tips
+- Start testing from shortest to deepest branch
+- Start refactoring from deepest to shortest branch
+
+![Working with Legacy Code Tips](img/tips.png)
+
+## Step by Step
+1. [Cover the production code](steps/1.cover-the-code.md)
+2. [Improve confidence in our tests](steps/2.mutate-some-code.md)
+3. [Refactor the production code](steps/3.refactoring.md)
+4. [Other refactorings](steps/4.other-refactorings.md)
+
+## What did we use / learn ?
+- `Seams`
+- `Automated refactoring` via our IDE
+  - Extract Method
+  - Change Signature
+  - Rename
+- `Mutation Testing`
+- Use `Higher Order Functions` to avoid duplication
+- Use `code coverage` as a driver
+- `Test Data Builder`
+- `Feature Envy`
+- `Sprout Class`
+- `TDD`
+
+Sources : 
+- [Nicolas Carlo - understand legacy code](https://understandlegacycode.com/blog/key-points-of-working-effectively-with-legacy-code/#identify-seams-to-break-your-code-dependencies)
+- [Sandro Mancuso - Testing legacy with Hard-wired dependencies](https://www.codurance.com/publications/2011/07/16/testing-legacy-hard-wired-dependencies)
+- [Micheal Feathers - Working Effectively with Legacy Code](https://www.oreilly.com/library/view/working-effectively-with/0131177052/)
+
+<a href="https://youtu.be/LSqbXorkyfQ" rel="Sandro's video">![Sandro's video](img/video.png)</a>