XCTest passes when it does not work with the wait

Question

I am testing a method that runs in the background and executes a block of code when it ends. I use expectations to handle asynchronous test execution. I wrote a simple test that shows the behavior:

- (void) backgroundMethodWithCallback: (void(^)(void)) callback {
    dispatch_queue_t backgroundQueue;
    backgroundQueue = dispatch_queue_create("background.queue", NULL);
    dispatch_async(backgroundQueue, ^(void) {
        callback();
    });
}

- (void) testMethodWithCallback {
    XCTestExpectation *expectation = [self expectationWithDescription:@"Add collection bundle"];
    [self backgroundMethodWithCallback:^{
        [expectation fulfill];

        usleep(50);
        XCTFail(@"fail test");
    }];
    [self waitForExpectationsWithTimeout: 2 handler:^(NSError *error) {
        if (error != nil) {
            XCTFail(@"timeout");
        }
    }];
}

The string XCTFail(@"fail test");should be unsuccessful for this test, but the test passes.

I also noticed that this only happens when the code executed on the callback takes some time (in my case, I checked some files on the file system). This is why the string is usleep(50);needed to reproduce the case.

Answer 1

. , :

- (void) testMethodWithCallback {
    XCTestExpectation *expectation = [self expectationWithDescription:@"Add collection bundle"];
    [self backgroundMethodWithCallback:^{

        usleep(50);
        XCTFail(@"fail test");
        [expectation fulfill];
    }];
    [self waitForExpectationsWithTimeout: 2 handler:^(NSError *error) {
        if (error != nil) {
            XCTFail(@"timeout");
        }
    }];
}

, Apple, fulfill , .

. swift, fulfill . , Objective-C.

Answer 2

, backgroundMethodWithCallback, , XCTFail. , , , . , XCTFail , .

, [expectation fulfill] , .