swift - 如果 XCTestExpectation 出乎意料怎么办

Question

我正在用 Swift 编写一个 XCTest 单元测试。这个想法是在特定情况下不得调用回调。

所以我做的是

func testThatCallbackIsNotFired() {

    let expectation = expectationWithDescription("A callback is fired")
    // configure an async operation

    asyncOperation.run() { (_) -> () in
        expectation.fulfill()    // if this happens, the test must fail
    }

    waitForExpectationsWithTimeout(1) { (error: NSError?) -> Void in

        // here I expect error to be not nil,
        // which would signalize that expectation is not fulfilled,
        // which is what I expect, because callback mustn't be called
        XCTAssert(error != nil, "A callback mustn't be fired")
    }
}

当回调被调用时，一切正常:它失败并显示消息“A callback mustn't be fired”，这正是我所需要的。

但是如果期望还没有实现，它就会失败并说

异步等待失败:超时超过 1 秒，预期未满足:“回调已触发”。

因为没有实现的期望是我所需要的，所以我不希望测试失败。

您有什么建议可以避免这种情况吗？或者，也许，我可以用不同的方式实现我的目标？谢谢。

Answer 1

在这篇文章中使用 isInverted https://www.swiftbysundell.com/posts/unit-testing-asynchronous-swift-code

class DebouncerTests: XCTestCase {
    func testPreviousClosureCancelled() {
        let debouncer = Debouncer(delay: 0.25)

        // Expectation for the closure we'e expecting to be cancelled
        let cancelExpectation = expectation(description: "Cancel")
        cancelExpectation.isInverted = true

        // Expectation for the closure we're expecting to be completed
        let completedExpectation = expectation(description: "Completed")

        debouncer.schedule {
            cancelExpectation.fulfill()
        }

        // When we schedule a new closure, the previous one should be cancelled
        debouncer.schedule {
            completedExpectation.fulfill()
        }

        // We add an extra 0.05 seconds to reduce the risk for flakiness
        waitForExpectations(timeout: 0.3, handler: nil)
    }
}