Rust Testing Patterns
Comprehensive Rust testing patterns for writing reliable, maintainable tests following TDD methodology.
When to Use
- Writing new Rust functions, methods, or traits
- Adding test coverage to existing code
- Creating benchmarks for performance-critical code
- Implementing property-based tests for input validation
- Following TDD workflow in Rust projects
How It Works
- Identify target code — Find the function, trait, or module to test
- Write a test — Use
#[test]in a#[cfg(test)]module, rstest for parameterized tests, or proptest for property-based tests - Mock dependencies — Use mockall to isolate the unit under test
- Run tests (RED) — Verify the test fails with the expected error
- Implement (GREEN) — Write minimal code to pass
- Refactor — Improve while keeping tests green
- Check coverage — Use cargo-llvm-cov, target 80%+
TDD Workflow for Rust
The RED-GREEN-REFACTOR Cycle
RED → Write a failing test first
GREEN → Write minimal code to pass the test
REFACTOR → Improve code while keeping tests green
REPEAT → Continue with next requirement
Step-by-Step TDD in Rust
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