Question

使用waitForExpectation随机崩溃，如果我在dispatch_after中满足期望的话。

它发生在objective-c和swift中。

完全随机，有时它有时不起作用。有谁有想法吗？（我在MacMini上使用CMD + U运行它，但我也尝试使用MBP Retina，结果相同）

示例代码：

func testBarcodeNotFound() {
        let exp = self.expectationWithDescription("store loading")
        OHHTTPStubs.stubRequestsPassingTest({ (request:NSURLRequest!) -> Bool in
            if request.URL.absoluteString == nil {
                return false
            }
            return request.URL.absoluteString!.hasSuffix("/products/barcode/1422/")
            }, withStubResponse: { (request:NSURLRequest!) -> OHHTTPStubsResponse! in
                let data = "".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)
                return OHHTTPStubsResponse(data: data, statusCode: 404, headers: ["Content-Type":"application/json"])

        })
        self.productsVC.scanningVC.successScan("1422", "EAN13")
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(0.5 * Double(NSEC_PER_SEC))), dispatch_get_main_queue()) { () -> Void in
            exp.fulfill()
        }

        self.waitForExpectationsWithTimeout(1, handler: nil)

        XCTAssertTrue(self.delegateForProductsVC.barcodeNotFoundCalled)

    }

并回溯

(lldb) bt
* thread #1: tid = 0x27e405, 0x06461ab0 libdispatch.dylib`_dispatch_semaphore_dispose + 92, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
    frame #0: 0x06461ab0 libdispatch.dylib`_dispatch_semaphore_dispose + 92
    frame #1: 0x06463578 libdispatch.dylib`_dispatch_dispose + 43
    frame #2: 0x064759e1 libdispatch.dylib`_os_object_dispose + 33
    frame #3: 0x06475cb1 libdispatch.dylib`-[OS_dispatch_object _xref_dispose] + 58
    frame #4: 0x064759bb libdispatch.dylib`_os_object_xref_dispose + 33
    frame #5: 0x05759eb1 libobjc.A.dylib`objc_release + 65
    frame #6: 0x2011949d XCTest`__destroy_helper_block_95 + 29
    frame #7: 0x064e4793 libsystem_sim_blocks.dylib`_Block_release + 211
    frame #8: 0x0647603f libdispatch.dylib`_dispatch_client_callout + 14
    frame #9: 0x0645f764 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 470
    frame #10: 0x05af095e CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 14
    frame #11: 0x05aaf760 CoreFoundation`__CFRunLoopRun + 2256
    frame #12: 0x05aaebcb CoreFoundation`CFRunLoopRunSpecific + 443
    frame #13: 0x05aae9fb CoreFoundation`CFRunLoopRunInMode + 123
    frame #14: 0x04c2ed98 Foundation`-[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 309
    frame #15: 0x20119a31 XCTest`-[XCTestCase(AsynchronousTesting) waitForExpectationsWithTimeout:handler:] + 1192
  * frame #16: 0x1055be0b SomeAppNative`SomeApp.ProductsDelegatesViewControllerTest.testBarcodeNotFound (self=0x7b0dbdf0)() -> () + 5595 at ProductsDelegatesViewControllerTest.swift:108
    frame #17: 0x1055c1a2 SomeAppNative`@objc SomeApp.ProductsDelegatesViewControllerTest.testBarcodeNotFound (SomeApp.ProductsDelegatesViewControllerTest)() -> () + 34 at ProductsDelegatesViewControllerTest.swift:0
    frame #18: 0x05a7976d CoreFoundation`__invoking___ + 29
    frame #19: 0x05a79618 CoreFoundation`-[NSInvocation invoke] + 360
    frame #20: 0x2010897b XCTest`-[XCTestCase invokeTest] + 320
    frame #21: 0x20108bb9 XCTest`-[XCTestCase performTest:] + 184
    frame #22: 0x20114162 XCTest`-[XCTest run] + 314
    frame #23: 0x20107598 XCTest`-[XCTestSuite performTest:] + 406
    frame #24: 0x20114162 XCTest`-[XCTest run] + 314
    frame #25: 0x20107598 XCTest`-[XCTestSuite performTest:] + 406
    frame #26: 0x20114162 XCTest`-[XCTest run] + 314
    frame #27: 0x20107598 XCTest`-[XCTestSuite performTest:] + 406
    frame #28: 0x20114162 XCTest`-[XCTest run] + 314
    frame #29: 0x20103de2 XCTest`__25-[XCTestDriver _runSuite]_block_invoke + 61
    frame #30: 0x20110c82 XCTest`-[XCTestObservationCenter _observeTestExecutionForBlock:] + 184
    frame #31: 0x20103d06 XCTest`-[XCTestDriver _runSuite] + 285
    frame #32: 0x20104951 XCTest`-[XCTestDriver _checkForTestManager] + 272
    frame #33: 0x20104c6b XCTest`-[XCTestDriver runTestSuite:completionHandler:] + 378
    frame #34: 0x2011775c XCTest`+[XCTestProbe runTests:] + 216
    frame #35: 0x04c2ab57 Foundation`__NSFireDelayedPerform + 423
    frame #36: 0x05af08d6 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 22
    frame #37: 0x05af025d CoreFoundation`__CFRunLoopDoTimer + 1309
    frame #38: 0x05aaf6ba CoreFoundation`__CFRunLoopRun + 2090
    frame #39: 0x05aaebcb CoreFoundation`CFRunLoopRunSpecific + 443
    frame #40: 0x05aae9fb CoreFoundation`CFRunLoopRunInMode + 123
    frame #41: 0x0712e24f GraphicsServices`GSEventRunModal + 192
    frame #42: 0x0712e08c GraphicsServices`GSEventRun + 104
    frame #43: 0x034518b6 UIKit`UIApplicationMain + 1526
    frame #44: 0x0053dae5 SomeApp`main(argc=16, argv=0xbff6e4a4) + 213 at main.m:16
    frame #45: 0x0649cac9 libdyld.dylib`start + 1
(lldb)

Answer 1

我遇到了类似的问题，我花了三天才弄明白。

-waitForExpectationsWithTimeout:handler:的文档说：

 * -waitForExpectationsWithTimeout:handler: runs the run loop while handling events until all expectations
 * are fulfilled or the timeout is reached. Clients should not manipulate the run
 * loop while using this API.

您的NSInputStream或NSOutputStream很可能在等待期间试图影响runloop，这会导致崩溃。

Answer 2

我有同样的问题。我的修复似乎是增加了超时间隔。我最初的超时间隔为1，并将其增加到5只是为了安全起见。似乎现在工作正常。我不确定您的异步调用需要多长时间，或者您是否可以承受超过1的超时间隔，但是值得一试。

Answer 3

当闭包存在于同一范围内时，Swift特别难以显示正确的异常断点。

我在使用dispatch_after的XCTestCase中看到了同样的问题，甚至通过异常断点与waitForExpectationsWithTimeout的行相同，因为对nil对象进行了向下转换，测试用例崩溃了。

我知道这不是你的情况但是每当发生这种情况时，我建议一次删除一行语句并在每次删除后运行测试。如果测试没有崩溃，你就已经确定了罪魁祸首。不幸的是，在撰写本文时，只要Swift在一行没有意义的行上显示异常断点，这是您在崩溃报告工具中可能会看到的臭名昭着的第0行。

如果您已经发现了崩溃，请告诉我们。

iOS测试因waitForExpectationsWithTimeout而崩溃

3 个答案: