Swift Testing

Swift Testing Standards

Priority: P0 (CRITICAL)

Write XCTest Cases

• Standard Naming: Test functions must prefixed by 'test' (e.g., func testUserLoginSuccessful()).
• Setup/Teardown: Use setUpWithError() and tearDownWithError() for environment management.
• Assertions: Use specific assertions: XCTAssertEqual, XCTAssertNil, XCTAssertTrue, etc.

See implementation examples for XCTest setup/teardown, async tests, and UI test patterns.

Test Async Code

• Async/Await: Mark test methods as async throws and use try await directly inside them.
• Expectations: Use XCTestExpectation for callback-based async logic. Call expectation then fulfill() when done; then wait(for: [exp], timeout: 2.0) to block.
• Timeout: Always set reasonable timeouts for expectations to avoid hanging CI.

Organize Test Suites

• Unit Tests: Use protocols for dependencies and inject them via constructor (e.g., init(service: ServiceProtocol)). Focus on logic isolation using mocks/stubs.
• UI Tests: Test user flows using XCUIApplication and accessibility identifiers.
• Coverage: Aim for high coverage on critical business logic and state transitions.

Anti-Patterns

• No Thread.sleep: Use expectations or await.
• No force unwrap in tests: Use XCTUnwrap() for better failure messages.
• No assertion-free tests: test that only runs code not test.

References

• XCTest Patterns & Async Tests

Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

• Inject them via constructor
• Use protocols
• prefixed by 'test'