测试 swift 异步函数超时

如何编写一个单元测试来检查异步函数是否不会超时？

我正在尝试常规XCTestExpectation， 但是因为await暂停一切，是等不到期待。

在下面的代码中，我正在检查loader.perform()执行时间不超过1秒。

func testLoaderSuccess() async throws {    
    let expectation = XCTestExpectation(description: "doesn't timeout")

    let result = try await loader.perform()

    XCTAssert(result.value == 42)

    wait(for: [expectation], timeout: 1) // execution never gets here

    expectation.fulfill()
}

如果任务超时，取消任务可能是明智的做法：

func testA() async throws {
    let expectation = XCTestExpectation(description: "timeout")

    let task = Task {
        let result = try await loader.perform()
        XCTAssertEqual(result, 42)
        expectation.fulfill()
    }

    await fulfillment(of: [expectation], timeout: 1)
    task.cancel()
}

如果你不，perform即使之后仍可能继续运行testA在失败场景中完成。

另一种方法是使用任务组：

func testB() async throws {
    try await withThrowingTaskGroup(of: Void.self) { group in
        group.addTask {
            let result = try await self.loader.perform()
            XCTAssertEqual(result, 42)
        }
        group.addTask {
            try await Task.sleep(for: .seconds(1))
            XCTFail("Timed out")
        }
        let _ = try await group.next() // wait for the first one
        group.cancelAll()              // cancel the other one
    }
}