Rust Testing

affaan-m/ECC/pi/core/skills/rust-testing

作者 affaan-mef648e01899ba3e8dc6371642deaaf64b4477775無授權條款275K 個星標收錄於 2026年10月9日更新於 2026年10月9日儲存庫4 天前更新

Rust testing patterns including unit tests, integration tests, async testing, property-based testing, mocking, and coverage. Follows TDD methodology. Use when writing Rust tests — unit, integration, async, property-based, or coverage.

僅含說明Software Development
AI 產生的概覽

指導撰寫 Rust 測試：單元、整合、非同步、屬性測試、模擬、基準與覆蓋率，遵循 TDD。

功能
此技能提供 Rust 測試模式與程式碼範例，涵蓋 #[cfg(test)] 模組中的單元測試、整合測試、使用 Tokio 的非同步測試、錯誤與 panic 測試、使用 rstest 的參數化測試、使用 proptest 的屬性測試、使用 mockall 的模擬、文件測試以及 Criterion 基準測試。它也說明 RED-GREEN-REFACTOR 的 TDD 流程，以及使用 cargo-llvm-cov 進行覆蓋率量測，包含建議的覆蓋率目標與 CI 步驟。此技能僅為說明性內容，本身不產生檔案或指令碼。
適用情境
適用於為 Rust 程式碼撰寫或補充測試、在 Rust 專案中遵循 TDD，或設定覆蓋率與 CI 測試步驟的情境。也適合需要非同步、屬性測試或模擬測試模式時使用。
執行需求
不含指令碼。範例假定已安裝 Rust 工具鏈與 cargo，並可選用 tokio、rstest、proptest、mockall、criterion 和 cargo-llvm-cov 等 crate 與工具。

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

  1. Identify target code — Find the function, trait, or module to test
  2. Write a test — Use #[test] in a #[cfg(test)] module, rstest for parameterized tests, or proptest for property-based tests
  3. Mock dependencies — Use mockall to isolate the unit under test
  4. Run tests (RED) — Verify the test fails with the expected error
  5. Implement (GREEN) — Write minimal code to pass
  6. Refactor — Improve while keeping tests green
  7. Check coverage — Use cargo-llvm-cov, target 80%+

TDD Workflow for Rust

The RED-GREEN-REFACTOR Cycle

RED     → Write a failing test firstGREEN   → Write minimal code to pass the testREFACTOR → Improve code while keeping tests greenREPEAT  → Continue with next requirement

Step-by-Step TDD in Rust

rust
// RED: Write test first, use todo!() as placeholderpub fn add(a: i32, b: i32) -> i32 { todo!() }
#[cfg(test)]mod tests {    use super::*;    #[test]    fn test_add() { assert_eq!(add(2, 3), 5); }}// cargo test → panics at 'not yet implemented'
rust
// GREEN: Replace todo!() with minimal implementationpub fn add(a: i32, b: i32) -> i32 { a + b }// cargo test → PASS, then REFACTOR while keeping tests green

Unit Tests

Module-Level Test Organization

rust
// src/user.rspub struct User {    pub name: String,    pub email: String,}
impl User {    pub fn new(name: impl Into<String>, email: impl Into<String>) -> Result<Self, String> {        let email = email.into();        if !email.contains('@') {            return Err(format!("invalid email: {email}"));        }        Ok(Self { name: name.into(), email })    }
    pub fn display_name(&self) -> &str {        &self.name    }}
#[cfg(test)]mod tests {    use super::*;
    #[test]    fn creates_user_with_valid_email() {        let user = User::new("Alice", "[email protected]").unwrap();        assert_eq!(user.display_name(), "Alice");        assert_eq!(user.email, "[email protected]");    }
    #[test]    fn rejects_invalid_email() {        let result = User::new("Bob", "not-an-email");        assert!(result.is_err());        assert!(result.unwrap_err().contains("invalid email"));    }}

Assertion Macros

rust
assert_eq!(2 + 2, 4);                                    // Equalityassert_ne!(2 + 2, 5);                                    // Inequalityassert!(vec![1, 2, 3].contains(&2));                     // Booleanassert_eq!(value, 42, "expected 42 but got {value}");    // Custom messageassert!((0.1_f64 + 0.2 - 0.3).abs() < f64::EPSILON);   // Float comparison

Error and Panic Testing

Testing Result Returns

rust
#[test]fn parse_returns_error_for_invalid_input() {    let result = parse_config("}{invalid");    assert!(result.is_err());
    // Assert specific error variant    let err = result.unwrap_err();    assert!(matches!(err, ConfigError::ParseError(_)));}
#[test]fn parse_succeeds_for_valid_input() -> Result<(), Box<dyn std::error::Error>> {    let config = parse_config(r#"{"port": 8080}"#)?;    assert_eq!(config.port, 8080);    Ok(()) // Test fails if any ? returns Err}

Testing Panics

rust
#[test]#[should_panic]fn panics_on_empty_input() {    process(&[]);}
#[test]#[should_panic(expected = "index out of bounds")]fn panics_with_specific_message() {    let v: Vec<i32> = vec![];    let _ = v[0];}

Integration Tests

File Structure

text
my_crate/├── src/│   └── lib.rs├── tests/              # Integration tests│   ├── api_test.rs     # Each file is a separate test binary│   ├── db_test.rs│   └── common/         # Shared test utilities│       └── mod.rs

Writing Integration Tests

rust
// tests/api_test.rsuse my_crate::{App, Config};
#[test]fn full_request_lifecycle() {    let config = Config::test_default();    let app = App::new(config);
    let response = app.handle_request("/health");    assert_eq!(response.status, 200);    assert_eq!(response.body, "OK");}

Async Tests

With Tokio

rust
#[tokio::test]async fn fetches_data_successfully() {    let client = TestClient::new().await;    let result = client.get("/data").await;    assert!(result.is_ok());    assert_eq!(result.unwrap().items.len(), 3);}
#[tokio::test]async fn handles_timeout() {    use std::time::Duration;    let result = tokio::time::timeout(        Duration::from_millis(100),        slow_operation(),    ).await;
    assert!(result.is_err(), "should have timed out");}

Test Organization Patterns

Parameterized Tests with rstest

rust
use rstest::{rstest, fixture};
#[rstest]#[case("hello", 5)]#[case("", 0)]#[case("rust", 4)]fn test_string_length(#[case] input: &str, #[case] expected: usize) {    assert_eq!(input.len(), expected);}
// Fixtures#[fixture]fn test_db() -> TestDb {    TestDb::new_in_memory()}
#[rstest]fn test_insert(test_db: TestDb) {    test_db.insert("key", "value");    assert_eq!(test_db.get("key"), Some("value".into()));}

Test Helpers

rust
#[cfg(test)]mod tests {    use super::*;
    /// Creates a test user with sensible defaults.    fn make_user(name: &str) -> User {        User::new(name, &format!("{name}@test.com")).unwrap()    }
    #[test]    fn user_display() {        let user = make_user("alice");        assert_eq!(user.display_name(), "alice");    }}

Property-Based Testing with proptest

Basic Property Tests

rust
use proptest::prelude::*;
proptest! {    #[test]    fn encode_decode_roundtrip(input in ".*") {        let encoded = encode(&input);        let decoded = decode(&encoded).unwrap();        assert_eq!(input, decoded);    }
    #[test]    fn sort_preserves_length(mut vec in prop::collection::vec(any::<i32>(), 0..100)) {        let original_len = vec.len();        vec.sort();        assert_eq!(vec.len(), original_len);    }
    #[test]    fn sort_produces_ordered_output(mut vec in prop::collection::vec(any::<i32>(), 0..100)) {        vec.sort();        for window in vec.windows(2) {            assert!(window[0] <= window[1]);        }    }}

Custom Strategies

rust
use proptest::prelude::*;
fn valid_email() -> impl Strategy<Value = String> {    ("[a-z]{1,10}", "[a-z]{1,5}")        .prop_map(|(user, domain)| format!("{user}@{domain}.com"))}
proptest! {    #[test]    fn accepts_valid_emails(email in valid_email()) {        assert!(User::new("Test", &email).is_ok());    }}

Mocking with mockall

Trait-Based Mocking

rust
use mockall::{automock, predicate::eq};
#[automock]trait UserRepository {    fn find_by_id(&self, id: u64) -> Option<User>;    fn save(&self, user: &User) -> Result<(), StorageError>;}
#[test]fn service_returns_user_when_found() {    let mut mock = MockUserRepository::new();    mock.expect_find_by_id()        .with(eq(42))        .times(1)        .returning(|_| Some(User { id: 42, name: "Alice".into() }));
    let service = UserService::new(Box::new(mock));    let user = service.get_user(42).unwrap();    assert_eq!(user.name, "Alice");}
#[test]fn service_returns_none_when_not_found() {    let mut mock = MockUserRepository::new();    mock.expect_find_by_id()        .returning(|_| None);
    let service = UserService::new(Box::new(mock));    assert!(service.get_user(99).is_none());}

Doc Tests

Executable Documentation

rust
/// Adds two numbers together.////// # Examples////// ```/// use my_crate::add;////// assert_eq!(add(2, 3), 5);/// assert_eq!(add(-1, 1), 0);/// ```pub fn add(a: i32, b: i32) -> i32 {    a + b}
/// Parses a config string.////// # Errors////// Returns `Err` if the input is not valid TOML.////// ```no_run/// use my_crate::parse_config;////// let config = parse_config(r#"port = 8080"#).unwrap();/// assert_eq!(config.port, 8080);/// ```////// ```no_run/// use my_crate::parse_config;////// assert!(parse_config("}{invalid").is_err());/// ```pub fn parse_config(input: &str) -> Result<Config, ParseError> {    todo!()}

Benchmarking with Criterion

toml
# Cargo.toml[dev-dependencies]criterion = { version = "0.5", features = ["html_reports"] }
[[bench]]name = "benchmark"harness = false
rust
// benches/benchmark.rsuse criterion::{black_box, criterion_group, criterion_main, Criterion};
fn fibonacci(n: u64) -> u64 {    match n {        0 | 1 => n,        _ => fibonacci(n - 1) + fibonacci(n - 2),    }}
fn bench_fibonacci(c: &mut Criterion) {    c.bench_function("fib 20", |b| b.iter(|| fibonacci(black_box(20))));}
criterion_group!(benches, bench_fibonacci);criterion_main!(benches);

Test Coverage

Running Coverage

bash
# Install: cargo install cargo-llvm-cov (or use taiki-e/install-action in CI)cargo llvm-cov                    # Summarycargo llvm-cov --html             # HTML reportcargo llvm-cov --lcov > lcov.info # LCOV format for CIcargo llvm-cov --fail-under-lines 80  # Fail if below threshold

Coverage Targets

Code TypeTarget
Critical business logic100%
Public API90%+
General code80%+
Generated / FFI bindingsExclude

Testing Commands

bash
cargo test                        # Run all testscargo test -- --nocapture         # Show println outputcargo test test_name              # Run tests matching patterncargo test --lib                  # Unit tests onlycargo test --test api_test        # Integration tests onlycargo test --doc                  # Doc tests onlycargo test --no-fail-fast         # Don't stop on first failurecargo test -- --ignored           # Run ignored tests

Best Practices

DO:

  • Write tests FIRST (TDD)
  • Use #[cfg(test)] modules for unit tests
  • Test behavior, not implementation
  • Use descriptive test names that explain the scenario
  • Prefer assert_eq! over assert! for better error messages
  • Use ? in tests that return Result for cleaner error output
  • Keep tests independent — no shared mutable state

DON'T:

  • Use #[should_panic] when you can test Result::is_err() instead
  • Mock everything — prefer integration tests when feasible
  • Ignore flaky tests — fix or quarantine them
  • Use sleep() in tests — use channels, barriers, or tokio::time::pause()
  • Skip error path testing

CI Integration

yaml
# GitHub Actionstest:  runs-on: ubuntu-latest  steps:    - uses: actions/checkout@v4    - uses: dtolnay/rust-toolchain@stable      with:        components: clippy, rustfmt
    - name: Check formatting      run: cargo fmt --check
    - name: Clippy      run: cargo clippy -- -D warnings
    - name: Run tests      run: cargo test
    - uses: taiki-e/install-action@cargo-llvm-cov
    - name: Coverage      run: cargo llvm-cov --fail-under-lines 80

Remember: Tests are documentation. They show how your code is meant to be used. Write them clearly and keep them up to date.

來源與署名

來源：affaan-m/ECC位於pi/core/skills/rust-testing提交ef648e0

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