swift-tdd-workflow

name	swift-tdd-workflow
description	Enforces test-driven development for Swift code using XCTest or Swift Testing.
activation	Load when writing tests, fixing bugs, or refactoring Swift code

Skill: swift-tdd-workflow

Overview

Enforces test-driven development for Swift code.

Red-Green-Refactor

1. Write a failing test that describes the desired behavior.
2. Write the minimal code to make the test pass.
3. Refactor while keeping all tests green.

Framework Detection

• If the project imports Testing or has .swift-testing in Package.swift → use Swift Testing.
• Otherwise default to XCTest.
• Both can coexist; prefer Swift Testing for new tests.

XCTest Patterns

• Subclass XCTestCase.
• Override setUp() and tearDown() for fresh state per test.
• Use XCTAssertEqual, XCTAssertTrue, XCTAssertThrowsError.
• For async tests in XCTest, mark the test method as async and use await.

Swift Testing Patterns

• Annotate test functions with @Test.
• Use #expect(actual == expected) for assertions.
• Group related tests with @Suite.
• Name tests descriptively: @Test("user service returns cached user").

Test Isolation

• No shared mutable state between tests.
• Each test gets a fresh instance of the system under test.
• Reset global singletons or in-memory stores in tearDown / deinit.

Mocking

• Create protocol stubs for dependencies.
• Never mock framework types directly (e.g. do not mock URLSession; wrap it in a protocol and mock that).

Coverage

• Minimum 80% coverage.
• Flag uncovered paths and require justification for exceptions.