Testing a Web Service

🎓 TUTORIAL | Complete example of testing a web service

Complete example of testing a web service with Chicago TDD Tools.

Project Structure

myservice/
├── src/
│   ├── main.rs
│   ├── handlers/
│   │   ├── users.rs
│   │   ├── orders.rs
│   │   └── auth.rs
│   └── models/
└── tests/
    ├── integration_tests.rs
    └── api_tests.rs

Testing Endpoints

Example: GET /users

#![allow(unused)]
fn main() {
test!(test_get_users, {
    let client = TestClient::new()?;

    // Act
    let response = client.get("/users")?;

    // Assert
    assert_eq!(response.status, 200);
    let users: Vec<User> = response.json()?;
    assert!(!users.is_empty());
});
}

Example: POST /users

#![allow(unused)]
fn main() {
test!(test_create_user, {
    let client = TestClient::new()?;

    let user_data = TestDataBuilder::new()
        .with_var("name", "Alice")
        .with_var("email", "alice@example.com")
        .build_json()?;

    // Act
    let response = client.post("/users", &user_data)?;

    // Assert
    assert_eq!(response.status, 201);  // Created
    assert_ok!(&response.json::<User>());
});
}

Example: Error Cases

#![allow(unused)]
fn main() {
test!(test_create_user_validation_error, {
    let client = TestClient::new()?;

    let invalid_data = TestDataBuilder::new()
        .with_var("email", "not_an_email")
        .build_json()?;

    // Act
    let response = client.post("/users", &invalid_data)?;

    // Assert
    assert_eq!(response.status, 400);  // Bad request
});
}

Testing with Real Database

Use integration tests with fixtures:

#![allow(unused)]
fn main() {
test!(test_with_database, {
    let fixture = TestFixture::new()?;

    // Fixture provides database connection
    let db = fixture.db_connection();

    // Create user in database
    let user = db.create_user("Alice", "alice@example.com")?;

    // Test retrieval
    let retrieved = db.get_user(user.id)?;
    assert_eq!(retrieved.name, "Alice");
});
}

Testing Authentication

#![allow(unused)]
fn main() {
test!(test_auth_required, {
    let client = TestClient::new()?;

    // No authentication
    let response = client.get("/protected")?;
    assert_eq!(response.status, 401);  // Unauthorized

    // With authentication
    let token = client.login("alice", "password")?;
    let response = client.get_with_auth("/protected", &token)?;
    assert_eq!(response.status, 200);
});
}

Best Practices

✅ Do:

• Test with real database (in tests)
• Test all HTTP methods (GET, POST, PUT, DELETE)
• Test error cases (400, 401, 404, 500)
• Test response structure
• Use fixtures for isolation

❌ Don't:

• Mock the entire HTTP layer
• Test framework code
• Hard-code full responses

Testing Workflow

# 1. Unit tests (fast)
cargo make test-unit

# 2. Integration tests (requires database)
cargo make test-integration

# 3. Full CI simulation
cargo make ci-local

See: Advanced Techniques

Next Steps

Learn more:

• Integration Testing with Docker - Test with real services
• Best Practices - Web service testing patterns
• CLI Application Testing - Compare with CLI testing
• Observability - Add OTEL instrumentation

Ready to build?

• Create a simple REST API
• Test each endpoint (GET, POST, PUT, DELETE)
• Test error cases and authentication