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503 lines
11 KiB
Markdown
503 lines
11 KiB
Markdown
---
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name: rust-testing
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description: Rust测试模式，包括单元测试、集成测试、异步测试、基于属性的测试、模拟和覆盖率。遵循TDD方法学。
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origin: ECC
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---
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# Rust 测试模式
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遵循 TDD 方法论编写可靠、可维护测试的全面 Rust 测试模式。
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## 何时使用
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* 编写新的 Rust 函数、方法或特征
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* 为现有代码添加测试覆盖率
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* 为性能关键代码创建基准测试
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* 为输入验证实现基于属性的测试
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* 在 Rust 项目中遵循 TDD 工作流
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## 工作原理
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1. **识别目标代码** — 找到要测试的函数、特征或模块
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2. **编写测试** — 在 `#[cfg(test)]` 模块中使用 `#[test]`，使用 rstest 进行参数化测试，或使用 proptest 进行基于属性的测试
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3. **模拟依赖项** — 使用 mockall 来隔离被测单元
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4. **运行测试 (RED)** — 验证测试是否按预期失败
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5. **实现 (GREEN)** — 编写最少代码以通过测试
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6. **重构** — 改进代码同时保持测试通过
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7. **检查覆盖率** — 使用 cargo-llvm-cov，目标 80% 以上
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## Rust 的 TDD 工作流
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### RED-GREEN-REFACTOR 循环
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```
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RED → 先写一个失败的测试
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GREEN → 编写最少代码使测试通过
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REFACTOR → 重构代码，同时保持测试通过
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REPEAT → 继续下一个需求
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```
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### Rust 中的分步 TDD
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```rust
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// RED: Write test first, use todo!() as placeholder
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pub fn add(a: i32, b: i32) -> i32 { todo!() }
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_add() { assert_eq!(add(2, 3), 5); }
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}
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// cargo test → panics at 'not yet implemented'
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```
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```rust
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// GREEN: Replace todo!() with minimal implementation
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pub fn add(a: i32, b: i32) -> i32 { a + b }
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// cargo test → PASS, then REFACTOR while keeping tests green
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```
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## 单元测试
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### 模块级测试组织
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```rust
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// src/user.rs
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pub struct User {
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pub name: String,
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pub email: String,
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}
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impl User {
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pub fn new(name: impl Into<String>, email: impl Into<String>) -> Result<Self, String> {
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let email = email.into();
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if !email.contains('@') {
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return Err(format!("invalid email: {email}"));
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}
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Ok(Self { name: name.into(), email })
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}
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pub fn display_name(&self) -> &str {
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&self.name
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn creates_user_with_valid_email() {
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let user = User::new("Alice", "alice@example.com").unwrap();
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assert_eq!(user.display_name(), "Alice");
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assert_eq!(user.email, "alice@example.com");
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}
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#[test]
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fn rejects_invalid_email() {
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let result = User::new("Bob", "not-an-email");
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assert!(result.is_err());
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assert!(result.unwrap_err().contains("invalid email"));
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}
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}
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```
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### 断言宏
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```rust
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assert_eq!(2 + 2, 4); // Equality
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assert_ne!(2 + 2, 5); // Inequality
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assert!(vec![1, 2, 3].contains(&2)); // Boolean
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assert_eq!(value, 42, "expected 42 but got {value}"); // Custom message
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assert!((0.1_f64 + 0.2 - 0.3).abs() < f64::EPSILON); // Float comparison
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```
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## 错误与 Panic 测试
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### 测试 `Result` 返回值
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```rust
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#[test]
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fn parse_returns_error_for_invalid_input() {
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let result = parse_config("}{invalid");
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assert!(result.is_err());
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// Assert specific error variant
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let err = result.unwrap_err();
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assert!(matches!(err, ConfigError::ParseError(_)));
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}
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#[test]
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fn parse_succeeds_for_valid_input() -> Result<(), Box<dyn std::error::Error>> {
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let config = parse_config(r#"{"port": 8080}"#)?;
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assert_eq!(config.port, 8080);
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Ok(()) // Test fails if any ? returns Err
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}
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```
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### 测试 Panic
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```rust
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#[test]
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#[should_panic]
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fn panics_on_empty_input() {
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process(&[]);
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}
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#[test]
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#[should_panic(expected = "index out of bounds")]
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fn panics_with_specific_message() {
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let v: Vec<i32> = vec![];
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let _ = v[0];
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}
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```
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## 集成测试
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### 文件结构
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```text
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my_crate/
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├── src/
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│ └── lib.rs
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├── tests/ # 集成测试
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│ ├── api_test.rs # 每个文件都是一个独立的测试二进制文件
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│ ├── db_test.rs
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│ └── common/ # 共享测试工具
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│ └── mod.rs
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```
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### 编写集成测试
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```rust
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// tests/api_test.rs
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use my_crate::{App, Config};
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#[test]
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fn full_request_lifecycle() {
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let config = Config::test_default();
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let app = App::new(config);
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let response = app.handle_request("/health");
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assert_eq!(response.status, 200);
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assert_eq!(response.body, "OK");
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}
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```
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## 异步测试
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### 使用 Tokio
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```rust
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#[tokio::test]
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async fn fetches_data_successfully() {
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let client = TestClient::new().await;
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let result = client.get("/data").await;
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assert!(result.is_ok());
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assert_eq!(result.unwrap().items.len(), 3);
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}
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#[tokio::test]
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async fn handles_timeout() {
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use std::time::Duration;
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let result = tokio::time::timeout(
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Duration::from_millis(100),
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slow_operation(),
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).await;
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assert!(result.is_err(), "should have timed out");
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}
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```
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## 测试组织模式
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### 使用 `rstest` 进行参数化测试
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```rust
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use rstest::{rstest, fixture};
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#[rstest]
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#[case("hello", 5)]
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#[case("", 0)]
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#[case("rust", 4)]
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fn test_string_length(#[case] input: &str, #[case] expected: usize) {
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assert_eq!(input.len(), expected);
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}
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// Fixtures
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#[fixture]
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fn test_db() -> TestDb {
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TestDb::new_in_memory()
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}
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#[rstest]
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fn test_insert(test_db: TestDb) {
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test_db.insert("key", "value");
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assert_eq!(test_db.get("key"), Some("value".into()));
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}
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```
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### 测试辅助函数
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```rust
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#[cfg(test)]
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mod tests {
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use super::*;
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/// Creates a test user with sensible defaults.
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fn make_user(name: &str) -> User {
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User::new(name, &format!("{name}@test.com")).unwrap()
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}
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#[test]
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fn user_display() {
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let user = make_user("alice");
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assert_eq!(user.display_name(), "alice");
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}
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}
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```
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## 使用 `proptest` 进行基于属性的测试
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### 基本属性测试
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```rust
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use proptest::prelude::*;
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proptest! {
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#[test]
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fn encode_decode_roundtrip(input in ".*") {
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let encoded = encode(&input);
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let decoded = decode(&encoded).unwrap();
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assert_eq!(input, decoded);
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}
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#[test]
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fn sort_preserves_length(mut vec in prop::collection::vec(any::<i32>(), 0..100)) {
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let original_len = vec.len();
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vec.sort();
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assert_eq!(vec.len(), original_len);
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}
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#[test]
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fn sort_produces_ordered_output(mut vec in prop::collection::vec(any::<i32>(), 0..100)) {
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vec.sort();
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for window in vec.windows(2) {
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assert!(window[0] <= window[1]);
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}
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}
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}
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```
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### 自定义策略
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```rust
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use proptest::prelude::*;
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fn valid_email() -> impl Strategy<Value = String> {
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("[a-z]{1,10}", "[a-z]{1,5}")
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.prop_map(|(user, domain)| format!("{user}@{domain}.com"))
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}
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proptest! {
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#[test]
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fn accepts_valid_emails(email in valid_email()) {
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assert!(User::new("Test", &email).is_ok());
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}
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}
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```
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## 使用 `mockall` 进行模拟
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### 基于特征的模拟
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```rust
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use mockall::{automock, predicate::eq};
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#[automock]
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trait UserRepository {
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fn find_by_id(&self, id: u64) -> Option<User>;
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fn save(&self, user: &User) -> Result<(), StorageError>;
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}
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#[test]
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fn service_returns_user_when_found() {
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let mut mock = MockUserRepository::new();
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mock.expect_find_by_id()
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.with(eq(42))
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.times(1)
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.returning(|_| Some(User { id: 42, name: "Alice".into() }));
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let service = UserService::new(Box::new(mock));
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let user = service.get_user(42).unwrap();
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assert_eq!(user.name, "Alice");
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}
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#[test]
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fn service_returns_none_when_not_found() {
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let mut mock = MockUserRepository::new();
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mock.expect_find_by_id()
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.returning(|_| None);
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let service = UserService::new(Box::new(mock));
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assert!(service.get_user(99).is_none());
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}
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```
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## 文档测试
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### 可执行的文档
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````rust
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/// Adds two numbers together.
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///
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/// # Examples
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///
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/// ```
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/// use my_crate::add;
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///
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/// assert_eq!(add(2, 3), 5);
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/// assert_eq!(add(-1, 1), 0);
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/// ```
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pub fn add(a: i32, b: i32) -> i32 {
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a + b
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}
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/// Parses a config string.
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///
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/// # Errors
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///
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/// Returns `Err` if the input is not valid TOML.
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///
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/// ```no_run
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/// use my_crate::parse_config;
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///
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/// let config = parse_config(r#"port = 8080"#).unwrap();
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/// assert_eq!(config.port, 8080);
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/// ```
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///
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/// ```no_run
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/// use my_crate::parse_config;
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///
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/// assert!(parse_config("}{invalid").is_err());
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/// ```
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pub fn parse_config(input: &str) -> Result<Config, ParseError> {
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todo!()
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}
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````
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## 使用 Criterion 进行基准测试
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```toml
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# Cargo.toml
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[dev-dependencies]
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criterion = { version = "0.5", features = ["html_reports"] }
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[[bench]]
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name = "benchmark"
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harness = false
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```
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```rust
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// benches/benchmark.rs
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use criterion::{black_box, criterion_group, criterion_main, Criterion};
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fn fibonacci(n: u64) -> u64 {
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match n {
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0 | 1 => n,
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_ => fibonacci(n - 1) + fibonacci(n - 2),
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}
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}
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fn bench_fibonacci(c: &mut Criterion) {
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c.bench_function("fib 20", |b| b.iter(|| fibonacci(black_box(20))));
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}
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criterion_group!(benches, bench_fibonacci);
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criterion_main!(benches);
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```
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## 测试覆盖率
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### 运行覆盖率
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```bash
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# Install: cargo install cargo-llvm-cov (or use taiki-e/install-action in CI)
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cargo llvm-cov # Summary
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cargo llvm-cov --html # HTML report
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cargo llvm-cov --lcov > lcov.info # LCOV format for CI
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cargo llvm-cov --fail-under-lines 80 # Fail if below threshold
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```
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### 覆盖率目标
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| 代码类型 | 目标 |
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|-----------|--------|
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| 关键业务逻辑 | 100% |
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| 公共 API | 90%+ |
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| 通用代码 | 80%+ |
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| 生成的 / FFI 绑定 | 排除 |
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## 测试命令
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```bash
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cargo test # Run all tests
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cargo test -- --nocapture # Show println output
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cargo test test_name # Run tests matching pattern
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cargo test --lib # Unit tests only
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cargo test --test api_test # Integration tests only
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cargo test --doc # Doc tests only
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cargo test --no-fail-fast # Don't stop on first failure
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cargo test -- --ignored # Run ignored tests
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```
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## 最佳实践
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**应该做：**
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* 先写测试 (TDD)
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* 使用 `#[cfg(test)]` 模块进行单元测试
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* 测试行为，而非实现
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* 使用描述性测试名称来解释场景
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* 为了更好的错误信息，优先使用 `assert_eq!` 而非 `assert!`
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* 在返回 `Result` 的测试中使用 `?` 以获得更清晰的错误输出
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* 保持测试独立 — 没有共享的可变状态
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**不应该做：**
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* 在可以测试 `Result::is_err()` 时使用 `#[should_panic]`
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* 模拟所有内容 — 在可行时优先考虑集成测试
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* 忽略不稳定的测试 — 修复或隔离它们
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* 在测试中使用 `sleep()` — 使用通道、屏障或 `tokio::time::pause()`
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* 跳过错误路径测试
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## CI 集成
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```yaml
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# GitHub Actions
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test:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v4
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- uses: dtolnay/rust-toolchain@stable
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with:
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components: clippy, rustfmt
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- name: Check formatting
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run: cargo fmt --check
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- name: Clippy
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run: cargo clippy -- -D warnings
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- name: Run tests
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run: cargo test
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- uses: taiki-e/install-action@cargo-llvm-cov
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- name: Coverage
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run: cargo llvm-cov --fail-under-lines 80
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```
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**记住**：测试就是文档。它们展示了你的代码应如何使用。清晰编写并保持更新。
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