Property Based Testing: From Theory to Practice
summary
Property-based testing is presented using the JavaScript fast-check library to generate hundreds of inputs per property, run tests (e.g., 100 runs), and automatically shrink failures to minimal counterexamples. A concrete example applies generators to test a diff algorithm: generators produce random diff candidates, the test reconstructs original texts, runs the diff function, and asserts the result contains the target text and has no more lines than the candidate. The approach finds real bugs and edge cases (Jest/Jasmine/React regressions, oversized strings) at the cost of increased execution time but with small, actionable failing cases.
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chapters (6)
- 0:00Introduction
- 5:10Speaker background
- 9:06What is property based testing
- 12:57Example with diffs
- 23:19Applications and limits
- 26:07Q&A
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