Migrating to Jest test runner

I have already shared my comparison of two JavaScript testing solutions where I admitted that I favor Jest over Mocha. Back then, I listed all major differences between those tools summarized with advantages and disadvantages of migrating to Jest:

Pros:

  • Simpler API, less boilerplate code.
  • Flexible and easy configuration.
  • Test files executed in isolation.
  • Advanced watch mode.
  • Snapshots support = easier start with testing.
  • Code coverage.

Cons:

  • Another migration.
  • Mocha has still a bit better performance (according to my quick tests).

My analysis got very positive feedback, with only a few little concerns, so I got encouraged to take action and verify the assumptions stated. I picked two different projects to play with to ensure both of them will uniformly benefit from using Jest.

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Different types of software testing

Software testing helps protect code from incoming bugs and improves general quality of the functionalities exposed to the users. When you look at it from the developer’s standpoint the first thing that comes to mind is unit testing. However it turns out tests come in many flavors. I have already shared in the recap from Advanced TDD workshop with Uncle Bob what kinds of tests a professional team should use to ensure that the application remains intact. The following items create a hierarchy:

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Picking Jest over Mocha – testing tools comparison

At Automattic we use Mocha to run all tests written for Calypso project which powers WordPress.com. It also includes end-to-end tests, which live in their own repository. We have been using this setup for over 3 years now. I think it is a good moment to revisit this choice. I found this unit testing tools comparison very helpful when evaluating alternatives. I strongly agree with the conclusions shared by Martin Olsson in his article:

Staying with Javascript, I think it’s hard to ignore the momentum behind Jest. I would be awesome if someone fixed #2059 though. Then again, Mocha seems to work well enough for a lot of people.

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Recap: Advanced TDD workshop with Uncle Bob

Earlier this week I attended a three day Advanced TDD workshop delivered by Uncle Bob Martin. The course explained the principles and practices of Test-driven development as described in his book, Agile Software Development, Principles, Patterns, and Practices. It was an amazing experience, packed with great knowledge, so I couldn’t resist sharing my notes.

Uncle Bob (Robert C. Martin):

He has been a programmer since 1970. He is the Master Craftsman at 8th Light inc, an acclaimed speaker at conferences worldwide, and the author of many books including: The Clean Coder, Clean Code, Agile Software Development: Principles, Patterns, and Practices, and UML for Java Programmers.
– Skills Matter

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