rust-testing

Rust Testing Best Practices Comprehensive testing guide for Rust applications, covering CLI testing, library testing, async patterns, and CI integration. Contains 42 rules across 8 categories, prioritized by impact to guide test design, mocking strategies, and CI optimization. When to Apply Reference these guidelines when: Writing unit tests for Rust libraries or modules Creating integration tests for CLI applications Setting up mocking with mockall or trait-based design Testing async code with Tokio Configuring CI pipelines for Rust projects Rule Categories by Priority Priority Category Impact Prefix 1 Test Organization CRITICAL org- 2 Mocking and Test Doubles CRITICAL mock- 3 Async Testing HIGH async- 4 Property-Based Testing HIGH prop- 5 Test Fixtures and Setup MEDIUM fix- 6 Assertions and Error Testing MEDIUM assert- 7 CI Integration MEDIUM ci- 8 Test Performance LOW-MEDIUM perf- Quick Reference 1. Test Organization (CRITICAL) org-unit-test-modules - Use cfg(test) modules for unit tests org-integration-tests-directory - Place integration tests in tests directory org-shared-test-utilities - Use tests/common/mod.rs for shared utilities org-binary-crate-pattern - Extract logic from main.rs into lib.rs org-test-naming - Name tests after behavior not implementation org-test-cli-with-assert-cmd - Use assert_cmd for CLI testing 2. Mocking and Test Doubles (CRITICAL) mock-trait-based-design - Design for testability with traits mock-automock-attribute - Use mockall automock for complex mocking mock-avoid-mocking-owned-types - Avoid mocking types you own mock-expect-call-counts - Verify mock call counts explicitly mock-predicate-arguments - Use predicates to verify mock arguments mock-returning-sequences - Use sequences for multiple return values mock-static-methods - Use mock! macro for static methods 3. Async Testing (HIGH) async-tokio-test-macro - Use tokio::test for async test functions async-time-control - Use paused time for timeout testing async-mock-io - Use tokio_test for mocking async IO async-spawn-blocking - Test spawn_blocking with multi-threaded runtime async-test-channels - Use channels for testing async communication 4. Property-Based Testing (HIGH) prop-proptest-basics - Use proptest for property-based testing prop-custom-strategies - Create custom strategies for domain types prop-shrinking - Use shrinking to find minimal failing cases prop-invariant-testing - Test invariants instead of specific values 5. Test Fixtures and Setup (MEDIUM) fix-rstest-fixtures - Use rstest fixtures for test setup fix-rstest-parametrized - Use rstest case for parameterized tests fix-temp-directories - Use TempDir for file system tests fix-test-context - Use test-context for setup and teardown fix-once-cell-shared-state - Use OnceCell for expensive shared setup 6. Assertions and Error Testing (MEDIUM) assert-specific-errors - Assert specific error types not just is_err assert-should-panic - Use should_panic for panic testing assert-debug-display - Implement Debug for clear failure messages assert-custom-messages - Add context to assertions with custom messages assert-floating-point - Use approximate comparison for floating point assert-collection-contents - Assert collection contents not just length 7. CI Integration (MEDIUM) ci-cargo-nextest - Use cargo-nextest for faster CI ci-caching - Cache Cargo dependencies in CI ci-test-isolation - Ensure test isolation in parallel CI ci-coverage - Generate coverage reports in CI 8. Test Performance (LOW-MEDIUM) perf-compile-time - Reduce test compilation time perf-test-filtering - Filter tests for faster feedback loops perf-avoid-io-in-unit-tests - Avoid real IO in unit tests perf-parallel-test-execution - Configure parallel test threads perf-benchmark-critical-paths - Benchmark critical paths with Criterion How to Use Read individual reference files for detailed explanations and code examples: Section definitions - Category structure and impact levels Rule template - Template for adding new rules Reference Files File Description references/_sections.md Category definitions and ordering assets/templates/_template.md Template for new rules metadata.json Version and reference information