Description

The Refuctored Vending Machine is exercise code we have used in a number of courses. The codebase is tiny, but difficult enough to clean up. You can clone this repository and play around with refactorings to see if you can make it better.

We have provided a few integration tests, that test the vending machine from the outside.

Goals

We wanted a small volume of code that is difficult enough to clean up, so that you need to diligently find smells and apply refactorings in small steps, but not too big to get lost in.

Practicing coding skills on a sample problem works, because you can focus on one thing to learn, and you don't have to worry about deadlines or other problems your production code has. It's also easier to compare notes with others who did the same exercise - we find it insightful to observe how others attack a problem.

We also want to let you experience the effects of having a partial safety net. Therefore we have provided a few rough integration tests, that cover most of the code, but not everything! So be careful.

How to use

You might want to make a branch for each attempt you make, and commit whenever the tests are green, so you can compare your progress to the original goal, and see what line of attack works better or worse for you.

A sample commit comment might look like: 'smell: duplicate code. refactoring: extract method'.

If you can't find small enough steps, you might also consider committing partway through big steps, so you can choose where to go back to.

In general, if you can't come up with a small step, think harder or try to attack smells where you can find small refactorings for. We often start with simple rename refactorings: rename variables to understand what a piece of code does, rename methods to make it more clear what a method does, etcetera.

Steps:

1. Make a list of smells you find in the code. Put the smells you want to attack first on top.
2. Find appropriate refactorings and put them next to the smells. You may need multiple refactorings to resolve a smell.
3. Perform the refactorings for your worst smell.
4. Look at any new smells you introduced while refactoring.
5. Repeat.

We recommend that you run the provided tests often, even if they don't cover everything. Adding new tests is also a good idea, but that may only be possible after you've done some refactoring.

Prerequisites, testing & running

First install dependencies:

npm install

And then run all unit tests continuously:

npm-watch test

Which smells and refactorings can help me?

You can find lists of code smells and refactorings to choose from at:

• Code smells
• Catalog of refactorings

or you can order a pack of smells and refactoring cue cards to play with the smells and refactorings spatially.

References

• William F. Opdyke, Refactoring OO Frameworks (1992)
• Martin Fowler, Refactoring (1999 / 2019)
• Joshua Kerievsky, Refactoring to Patterns (2004)
• Wiliam C. Wake, Refactoring Workbook (2003)
• Sven Gorts, Refactoring Thumbnails

Authors

Marc Evers, Rob Westgeest, Willem van den Ende
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