Neal Brooks
Proton
Neal Brooks is a software engineer at Proton AG, where he works on helping to scale privacy-focused web services in order to create a better internet for everybody. He loves to uplift others through teaching, mentoring, and fostering positive culture. Neal is passionate about Domain-Driven Design, Test-Driven Development, and many other TLAs. As far as he knows, he is not related in any way to James Brooks.
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The Absolute Beginner’s Guide To Mutation Testing
King Vault - 13.30
Have you ever sweated away for months and finally achieved 100% coverage, but your customers still complained about bugs? Do you never feel satisfied that you can fully rely on your tests, even though you have data providers with all sorts of weird values in them? Are you certain that at least one test would fail if you introduced an error into any given line of code in the codebase? Do you have less than 100% confidence in your test suite?
How can you be sure that the code your colleague wants to merge to `main` via the `super-new-feature-branch` is adequately tested beyond the ‘coveralls’ report?
I’ll guide you on your first steps, as we:
- See why coverage alone is not a decent indicator of correctness or quality of our tests
- Learn how to improve confidence in our test suites by adding a new metric, the MSI
- Dig into how Infection works by mutating PHP’s Abstract Syntax Tree
- Install and run Infection on a codebase, then find and fix some escaped mutants
- * End with some personal advice on approaches which naturally lead to a higher initial MSI Soon you’ll be catching bugs that your team hasn't even written yet!
