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Refactoring Golf

https://github.com/sf105/refactoring-golf

Refactoring Golf is a game designed to stretch your refactoring muscles and to get you to explore your IDE to see what's really possible using shortcuts and automation. The idea is to focus on one aspect of coding and see how far it can be pushed.

This repository contains multiple versions of a simple class to calculate tax on a payslip.

  • The first 5,000 is tax free
  • Up to 20,000 is taxed at 10%
  • Up to 40,000 is taxed at 20%
  • Above 40,000 is taxed at 40%

Each version is a refactoring of the previous version. Sticking with the golf metaphor, each version is called a "hole".

Your goal is to refactor from each hole to the next safely and efficiently, using the features of the IDE with as few "strokes" as possible, where a stroke is an action that changes the code. Every stroke costs you points.

Your pairing partner should carefully score you as follows:

  • 0 points for formatting and selection
  • 1 point for every change made to the code using a shortcut or automated IDE feature (e.g., an automated refactoring, code template, rename, or Find/Replace)
  • 2 points for every manual edit. Note that a single "edit" could cover multiple lines of code.
  • There is a double points penalty for changes that leave the code failing the tests or not compiling.

Allow yourselves a maximum of 2 attempts at each round to determine your best score.

Hints

  • Each version has a notes.md file that describes the motivation for the next refactoring.
  • You might want to keep the target code open in another window, or perhaps on the partner's machine. It's easy to get confused about which file is which.
  • Commit your code frequently, especially after each refactoring stage. That will make rolling-back easier if you want to make another attempt or if you get confused.
  • Run the tests after each "stroke". You can do this by selecting the top-level refactoring-golf in the project view and selecting Run 'All Tests' from the pop-up menu.
  • Check your code in frequently so it's easier to try a refactoring more than once. Idea also has an excellent Local History option.
  • Also look at the options available from Show Context Action if you right-click on a feature. The (very useful) keyboard shortcut varies by platform.

Practical

  • This exercise was written with Intellj Idea. You should be able to clone the repository and Open it as a project.
  • You might have to set the JDK for the project. The project will build with versions from Java 11.
  • Idea has a Keymap Reference available from the help menu. If you're unfamiliar, it's worth reading this through and keeping it handy
  • Mouse actions are fine to start with, but learn the key shortcuts

Example scores

These are some example scores, achieved using IntelliJ.

HoleBest scoreNotes
1 6
2 3
3 9
4 17 lots of manual edits
5 13
6 14
7 29 This one is quite hard, but is possible
8 8
9 xx

Alternative version

There's an alternative version that was implemented using TDD from scratch in the reimplemented-with-tdd branch of the repository.

Acknowledgements

This exercise was mainly taken from an example by Lance Walton.

Other ideas were taken from David Denton and Ivan Sanchez, inspired by @ivanmoore and @rchatley

These instructions were mostly stolen from @jasongorman's Refactoring Golf.

Notes

  • we used long for the calculations, like the alternative TDD version. Both should probably use a decimal format.