Property-based testing in Android - are we testing like it's 1999?
summary
Argues that property-based testing catches faults value tests miss, demonstrating on a simple myMax function where Kotest (formerly KotlinTest) generators find a counterexample to a bad implementation, and showing ViewModel properties that replace three filter-specific unit tests with one rule that the add-button visibility equals filter==ALL. Uses checkAll/gen/arb/exhaustive generators, mocks and Mockito to capture LiveData emissions, converts JUnit rules to Kotest test listeners, and shows JUnit4 theories plus a custom RandomSupplier so property tests work without new libraries.
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chapters (14)
- 0:00Introduction and modern testing
- 1:13History of JVM testing
- 6:08Testing stagnation in 2016
- 7:11What is property-based testing
- 8:15Simple example with myMax function
- 10:24Limitations of value-based testing
- 11:25Exploring Kotest property checks
- 13:56Writing idiomatic property-based tests
- 17:31Testing Android ViewModels
- 21:48Modeling ViewModel actions
- 23:15Property-based ViewModel assertions
- 26:09Testing LiveData over time
- 28:12Property-based testing in JUnit
- 32:08Summary and Q&A
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