Swift Testing Migration

Swift Testing for unit and integration tests; XCTest stays for UI tests under cmuxUITests/ (Swift Testing has no XCUIApplication support).

New tests

import Testing

@Suite
struct ExampleTests {
    @Test
    func computesValue() {
        #expect(1 + 1 == 2)
    }
}

Use try #require(...) when a value must be unwrapped before continuing.

XCTest conversion mapping

Convert in place only when an edit naturally crosses the file; do not bulk-rewrite untouched tests.

XCTest	Swift Testing
`XCTestCase` subclass	`@Suite struct` (or `@Suite final class` for a reference type)
`func testFoo()`	`@Test func foo()`
`XCTAssertEqual(a, b)`	`#expect(a == b)`
`XCTAssertTrue(cond)`	`#expect(cond)`
`XCTUnwrap(x)`	`try #require(x)`
`XCTFail("msg")`	`Issue.record("msg")`
`setUp()`	`init()` (async setup: `async init()`)
`tearDown()`	`deinit`

Parameterized tests

@Test(arguments: [
    ("input-a", "output-a"),
    ("input-b", "output-b"),
])
func formats(input: String, expected: String) {
    #expect(format(input) == expected)
}

Parallel execution

Tests run in parallel by default, including across suites. Prefer isolated temp directories and injected dependencies; use @Suite(.serialized) only when a suite genuinely needs ordering or guards shared mutable state.

Referenced from SKILL.md

SKILL.mdView in source ↗

40- **Tags** via `@Test(.tags(.something))` let CI and local runs filter selectively.41- Migrate an existing XCTest file in place only when an edit already crosses it. Mapping in [references/swift-testing-migration.md](references/swift-testing-migration.md).

SKILL.mdView in source ↗

49- [references/swift-testing-migration.md](references/swift-testing-migration.md): XCTest to Swift Testing conversion mapping.50- [references/regression-and-quality.md](references/regression-and-quality.md): deciding whether a test is behavioral enough.