XCTestExpectation似乎不适用于Task()

Question

我试图运行一个发出网络请求的测试actor，如果您在它还在请求时调用它，它将取消第一个请求并抛出一个CancellationError。我使用一个Task()来模拟它被异步两次调用，并且代码看起来运行得很好。我可以看到抛出的正确错误和正在执行的catch-block。下面是密码。

func testCancellation() async throws {
    //setup code

    let expectation = XCTestExpectation(description: "Cancellation Error thrown")
    let autocompleteHandler = AutocompleteHandler(session: session)
        
    Task() {
        do {
            let _ = try await autocompleteHandler.autocomplete(query: "Grizzly Bear")
        } catch {
            if error is CancellationError { expectation.fulfill() }
        }
    }
    Task() {
        do {
            let _ = try await autocompleteHandler.autocomplete(query: "Grizzly Bear")
        } catch {
            if error is CancellationError { expectation.fulfill() }
        }
    }
        
    wait(for: [expectation], timeout: 1)
}

在运行这个程序时，我会得到以下错误：

Asynchronous wait failed: Exceeded timeout of 1 seconds, with unfulfilled expectations: "Cancellation Error thrown".

但就像我说的。我可以看到catch-block正在执行，error是正确的类型，而expectation.fulfill()正在被调用。

Answer 1

在阅读了@Alexander的评论后，我意识到我确实不需要等待任何东西。我将代码重新格式化如下，现在它开始工作了。

func testCancellation() async {
    //Setup code

    let autocompleteHandler = AutocompleteHandler(session: session)
        
    async let first = autocompleteHandler.autocomplete(query: "Grizzly Bear")
    async let second = autocompleteHandler.autocomplete(query: "Grizzly Bear")
        
    do {
        let _ = [try await first, try await second]
        XCTFail("Should have thrown cancellation error")
    } catch {
        XCTAssert(error is CancellationError)
    }
}

这如预期的那样起作用。