modernize-tests

Modernize Tests

Apply when: user asks to modernize, update, migrate, supercharge, or convert their tests. XCTest should be migrated to Swift Testing when possible, existing Swift Testing tests should be evaluated to see if they could be better structured adopting newer features.

Do not apply when: user asks to write new tests from scratch (without existing XCTest code), user asks about XCTest features only, user only asks about test results or test running, user is asking to update tests to cover new functionality rather than updating the tests themselves, user is debugging test failures without mentioning migration, user has UI automation tests using XCUI* APIs (these cannot be migrated to Swift Testing).

Migration Reference

Imports

Replace import XCTest with import Testing. A file can import both if it contains mixed test content during incremental migration.

When removing import XCTest, check whether the file uses Foundation types (URL, CharacterSet, ProcessInfo, Data, etc.). XCTest re-exports Foundation, so add import Foundation if needed.

Test Classes to Suites

Remove XCTestCase inheritance. Prefer struct over class:

• final class FoodTruckTests: XCTestCase { ... } -> struct FoodTruckTests { ... }

setUp/tearDown to init/deinit

Replace override func setUp() with init() (can be async throws). Replace override func tearDown() with deinit. If deinit is needed, use actor or final class instead of struct (since structs have no deinit). Change stored properties to not use implicitly-unwrapped optional types, and move their initial assignment from setUp to either be initialized inline or, if the initialization is complex, in an initializer.

struct MyTests {
    var fixture = Fixture()
    mutating func `Fixture behaves as expected`() {
        #expect(fixture.doSomething())
    }
}

Avoid pulling instance variables into function bodies; this can cause noise. Swift Testing reinvokes the initializer fresh before each test runs. If the test mutates an instance variable with value semantics, you may need to mark the test function mutating.