How to Write Better Code Using Mutation Testing
summary
A practical demo of Mutant and Mutest shows automated mutation of real Ruby code against RSpec, turning fragile line coverage into tests that fail when meaningful changes occur and revealing 31 different conditions in a small permissions method. Examples include switching Date.parse to iso8601 vs Date.parse and replacing regex anchors and using the new match? performance method. The tools run incrementally (since a git revision, by test selector), find surprising mutations, and fit into CI.
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chapters (15)
- 0:00Intro
- 0:30Talk Outline
- 2:12Mutation Testing by Hand
- 7:55Internal API
- 11:48Hardening Regular Expressions
- 16:49X-Raying Legacy Code
- 18:43Thorough Test Coverage
- 22:50Incredible Dead Code Detection
- 25:43Code Simplification
- 31:43Learn more about Ruby
- 32:54Learn faster
- 33:14Improve your testing skills
- 33:55Introduce fewer regressions
- 34:32Write simpler code
- 35:00Mutation Testing on the Job
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