rust-testing

Testing & Quality

Rust testing patterns for CLI applications, libraries, and frameworks. This skill should be used when writing, reviewing, or refactoring Rust tests including unit tests, integration tests, mocking, async testing, and CI integration. Triggers on tasks involving Rust testing, cargo test, mockall, proptest, tokio test, or test organization.

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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

Other versions