rust-testing

# Rust Testing Skill ## When to Activate Activate this skill when: - Writing Rust unit tests - Creating integration tests - Working with doc tests - Setting up property-based testing - Running benchmarks ## Quick Commands ```bash # Run all tests cargo test # With output cargo test -- --nocapture # Run specific test cargo test test_user_create # Run tests in module cargo test auth:: # Run ignored tests cargo test -- --ignored # Doc tests only cargo test --doc # Integration tests only cargo test --test integration ``` ## Unit Tests (Same File) ```rust pub fn add(a: i32, b: i32) -> i32 { a + b } #[cfg(test)] mod tests { use super::*; #[test] fn test_add() { assert_eq!(add(2, 3), 5); } #[test] fn test_add_negative() { assert_eq!(add(-1, -1), -2); } } ``` ## Test Attributes ```rust #[test] fn regular_test() { } #[test] #[ignore] fn slow_test() { } // Skip unless --ignored #[test] #[should_panic] fn test_panic() { panic!("This should panic"); } #[test] #[should_panic(expected = "specific message")] fn test_panic_message() { panic!("specific message here"); } #[test] fn test_with_result() -> Result<(), String> { let result = some_operation()?; assert_eq!(result, expected); Ok(()) } ``` ## Assertions ```rust // Basic assert_eq!(1 + 1, 2); assert_ne!(1 + 1, 3); assert!(true); // With messages assert_eq!(result, expected, "values should match: got {}", result); // Pattern matching assert!(matches!(value, Pattern::Variant(_))); // Option/Result assert!(some_option.is_some()); assert!(some_result.is_ok()); ``` ## Integration Tests ```rust // tests/api_integration.rs use my_crate::{Config, Server}; #[test] fn test_server_startup() { let config = Config::default(); let server = Server::new(config); assert!(server.start().is_ok()); } ``` ## Directory Structure ``` project/ ├── Cargo.toml ├── src/ │ ├── lib.rs # Unit tests in #[cfg(test)] │ └── user.rs # Module with inline tests └── tests/ # Integration tests ├── common/ │ └── mod.rs # Shared utilities └── api_test.rs ``` ## Mocking with Traits ```rust pub trait UserRepository { fn find_by_id(&self, id: u64) -> Option<User>; } #[cfg(test)] mod tests { use super::*; use std::collections::HashMap; struct MockUserRepo { users: HashMap<u64, User>, } impl UserRepository for MockUserRepo { fn find_by_id(&self, id: u64) -> Option<User> { self.users.get(&id).cloned() } } #[test] fn test_user_service() { let mut users = HashMap::new(); users.insert(1, User { id: 1, email: "test@example.com".into() }); let repo = MockUserRepo { users }; let service = UserService::new(Box::new(repo)); let user = service.get_user(1).unwrap(); assert_eq!(user.email, "test@example.com"); } } ``` ## Async Testing (tokio) ```rust #[tokio::test] async fn test_async_operation() { let result = fetch_data().await; assert!(result.is_ok()); } #[tokio::test] async fn test_with_timeout() { let result = tokio::time::timeout( Duration::from_secs(5), slow_operation() ).await; assert!(result.is_ok()); } ``` ## Doc Tests ```rust /// Adds two numbers together. /// /// # Examples /// /// ``` /// use my_crate::add; /// let result = add(2, 3); /// assert_eq!(result, 5); /// ``` pub fn add(a: i32, b: i32) -> i32 { a + b } ``` ## Property-Based Testing (proptest) ```rust use proptest::prelude::*; proptest! { #[test] fn test_add_commutative(a: i32, b: i32) { prop_assert_eq!(add(a, b), add(b, a)); } } ``` ## Coverage ```bash # Using cargo-tarpaulin cargo install cargo-tarpaulin cargo tarpaulin --out Html # Using cargo-llvm-cov cargo install cargo-llvm-cov cargo llvm-cov --html ``` ## Related Resources See `AgentUsage/testing_rust.md` for complete documentation including: - Benchmarking with criterion - Setup/teardown patterns - Mockall crate usage - CI configuration