ios-testing

Approach: F.I.R.S.T-First, Production-Ready Tests -- Every test produced by this skill must be Fast, Isolated, Repeatable, Self-validating, and Thorough. Architecture changes to production code and improvements to the test suite both follow phased, low-risk PRs tracked in a refactoring/ directory.

iOS Swift Testing

Enterprise-grade testing skill covering 11 areas across all iOS architectures. Opinionated: prescribes Swift Testing (@Test/@Suite/#expect) for all new tests on Xcode 16+, protocol-based mocks with call tracking, F.I.R.S.T compliance checks on every generated test, and architecture-specific patterns for MVVM (UIKit+Combine, SwiftUI+@Observable), VIPER, and TCA.

Test Distribution Rule

Target: 90% unit tests (mocked, milliseconds) | 8% integration (real DB/network stub) | 2% UI (XCUITest). When in doubt, write a unit test.

F.I.R.S.T Principles

Principle	What it means	Violation signal
Fast	Unit tests should run in milliseconds. Avoid unnecessary waits.	Real URLSession, Thread.sleep, disk I/O
Isolated	Tests don't share state. Order doesn't matter.	static var, setUp skipped, test A breaks B
Repeatable	Same result on any machine, any time.	Date(), UUID(), random data, time zones
Self-validating	Pass or fail -- no log inspection.	print(result) with no assertion
Thorough	Happy path + error path + edge cases.	Only green-path tests, 0% error coverage

Quick Decision Trees

"Swift Testing or XCTest?"

Need UI testing?           -> XCTest (XCUITest) only
Need performance testing?  -> XCTest (measure {}) only
Need attachments?          -> XCTest only
Need ObjC support?         -> XCTest only
New unit/integration test? -> Swift Testing (preferred)
Existing XCTest?           -> Migrate incrementally, both coexist

"Which assertion macro?"

Soft check (report + continue)?     -> #expect(expr)
Hard precondition (halt on fail)?   -> try #require(expr)
Unwrap optional + use value?        -> let val = try #require(optional)
Check error thrown?                 -> #expect(throws: Type.self) { }
Check nothing thrown?               -> #expect(throws: Never.self) { }
Record unconditional failure?       -> Issue.record("msg")