WWDC24 Meet Swift Testing

New Zealand — Deer Park Heights Queenstown

• Building blocks 先了解核心概念
• Common workflows 討論幾種常見的工作流程，包括自定義測試或使用不同參數重複測試的方法。
• Swift Testing and XCTest 介紹 Swift Testing 和 XCTest 之間的相互關係
• Open source 這個新項目在開源社區中的角色

Building blocks

Test functions

• Annotated using @Test
• Can be global functions or methods in a type
• May be async or throws
• May be global actor-isolated (such as @MainActor )

以前使用 XCTest 要執行測試的 function 都要用 test 開頭命名，例如

func test_doSomething() throws { ... }

現在加上 @Test 就不用了

Expectations

Validate expected conditions

• Use #expect(...) to validate that an expected condition is true
• Accepts ordinary expressions and operators
• Captures source code and subexpression values upon failure

Required expectations

有時出現預期失敗，可能會希望提前結束測試，這時可以用 #require

• Use try #require(...) to stop the test if the condition is false

• Can unwrap optional values, and stop test when nil

Traits

• Add descriptive information about a test
• Customization whether a test runs
• Modify how a test behaves

Suites

• Group related test functions and suites
• Annotated using @Suite

Implicit for types containing @Test functions or suites

• Use init and deinit for set-up and tear-down logic, respectively
• Initialized once per instance @Test method

以前我們使用 XCTest 都用 class，例如

final class SomeTests: XCTestCase { ... }

現在建議使用 struct

Common workflows

Tests with conditions

Runtime conditions

Controlling when tests run

• Specify a runtime-evaluated condition for a test using .enabled(if:...)
• Test will be skipped if condition is false

• Unconditionally disable a test using .disabled(...)
• Comment describing reason is included in results
• 這個方法比註解掉測試碼更好，因為他會驗證測試內的程式碼是否可編譯。

• Pair any trait with .bug(...) to reference an issue in a bug-tracking system

• Use @available(...) to specify an OS availability condition

• Use @available(...) instead of checking at runtime using #available(...)

Tests with common characteristics

利用 .tag(...) ，在左邊導航列可以找到相關被 tag 的測試，各 function 也可以在 @Test 上加 .tag

進階一點可以額外寫一個 struct 把 tag 寫在這層，原本各自 function 內的 tag 就可以移除了

Test Tags

Associate tests which have things in common to:

• Run all tests with a specific tag
• Filter by tag or see insights in Test Report

Shared among tests anywhere in a project

Tags can be local to a project or shared

擴充 Tag

extension Tag {

    @Tag static var formatting: Self

    @Tag static var networking: Self

}

Recommended practices

Prefer tags over test names when including/excluding in a Test Plan

Use the most appropriate trait type

• Example: .enabled(if: ...) instead of .tags(...) to represent a condition

更進階的用法可以看 Go further with Swift Testing WWDC24

Tests with different arguments

假如我們有許多內容很像的測試，只是某部分參數不同，這時候就很適合用 Parameterized Tests「參數化測試」

優化後

再來一個例子，以下這個做法用 for-loop 循環重複多次單個測試，但這個做法不是最好的，最好就是用 parameterized test function

優化後

Parameterized testing

• View details of each argument in results
• Re-run individual arguments to debug
• Run arguments in parallel

更進階的用法可以看

Go further with Swift Testing WWDC24

https://developer.apple.com/wwdc24/10195

Swift Testing and XCTest

鼓勵使用 struct，因為是 value type，這樣做可以避免無意的狀態共享而導致的錯誤

Migrating from XCTest
✅ Recommended practices

• Share a single unit test target
• • Swift Testing tests can coexist with XCTests
• Consolidate similar XCTests into a parameterized test
• Migrate each XCTest class with only one test method to a global @Test function
• Remove redundant “test” prefix from method names

⚠️ Supported functionality
Continue using XCTest for tests which:

• Use UI automation APIs (such as XCUIApplication )
• Use performance testing APIs (such as XCTMetric )
• Can only be written in Objective-C

Avoid calling XCTAsssert(...) from Swift Testing tests, or #expect(...) from XCTests

更多細節可參考 Migrating a test from XCTest

Open source

它可以用於

• Apple Platforms
• Linux
• Windows

而且在這些平台上都有通用的程式碼庫

Wrap-up

• Improve quality with Swift Testing
• Customize tests with traits
• Contribute in open source

最後可以了解更多細節 Go further with Swift Testing WWDC24

參考

• https://wwdcnotes.com/documentation/wwdcnotes/wwdc24-10179-meet-swift-testing/
• https://leocoout.medium.com/welcome-swift-testing-goodbye-xctest-7501b7a5b304
• https://developer.apple.com/documentation/testing/migratingfromxctest
• https://developer.apple.com/videos/play/wwdc2024/10179/
• https://www.youtube.com/watch?v=WFnkNcvLnCI