modernize-tests

Modernize Tests Patterns

Use this skill to migrate XCTest to Swift Testing and to modernize existing Swift Testing code. Assertion mappings, error and async patterns, setUp/tearDown conversion, and guidelines live in references/migration-reference.md; read it before editing.

When to Use

• User asks to migrate XCTest to Swift Testing
• Existing Swift Testing tests use outdated patterns or loop over inputs instead of parameterized tests
• Converting XCTestExpectation, XCTSkip, XCTExpectFailure, or XCTAttachment
• Converting setUp/tearDown to init/deinit

When NOT to Use

• UI tests using XCUIAutomation - they must remain XCTest
• XCTests using measure { ... } performance APIs - they cannot migrate (other methods in the same class can)
• Task is web or Python testing - use unit-testing or python-testing via WORKFLOW routing

Delivery Workflow

Use the checklist below and track progress:

Test modernization progress:
- [ ] Step 1: List XCTest classes and classify migratable vs. must-stay XCTest
- [ ] Step 2: Migrate one test class at a time using the reference mappings
- [ ] Step 3: Preserve `continueAfterFailure` semantics with `try #require`
- [ ] Step 4: Build and run tests; confirm no test was dropped

Core Rules

• Migrate one test class at a time; a file may hold both XCTest and Swift Testing during migration.
• Prefer struct suites; use actor or final class only when deinit is needed.
• Do not turn try #require into #expect; that changes behavior.
• Add @MainActor only where XCTest's implicit main-actor isolation was relied on; add @Suite(.serialized) for shared mutable state.
• Use only public API; never introduce underscore-prefixed symbols such as #_sourceLocation.
• Convert repeated-logic tests to @Test(arguments:).
• Add import Foundation when removing import XCTest if Foundation types are used.

Full mappings: references/migration-reference.md.

Anti-Patterns to Avoid

Anti-Pattern	Instead Do
Migrating UI or measure {} tests	Leave them as XCTest
Replacing try #require with #expect	Keep #require to preserve early exit
Adding @MainActor everywhere	Only where isolation was relied on
Keeping implicitly-unwrapped properties from setUp	Initialize inline or in init