Break point in XCTestCase can't be reached - ios

Question

I have a method that requests data from network , and I want to unit test it. But when I set a break point in the test case , the break point won't get there.
The method to be tested:
- (void)requestSuperDecisionDataWithCompletionHandler:(void (^)(NSArray *result))callBack {
static vector<vector<string>> arr;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//request data from network
IceNetwork::Init()->GetSuperDecision(arr);
if (arr.size() != kSuperDecisionDataCount) {
callBack(nil);
} else {
NSArray *convertedData = [self convertCArrayToNSArrayWithCArray:arr];
dispatch_async(dispatch_get_main_queue(), ^{
callBack(convertedData);
});
}
});
}
Test case:
- (void)testThatRequestSuperDecisionDataShouldReturnZeroOr14Items
{
//super decision
[_requestManager requestSuperDecisionDataWithCompletionHandler:^(NSArray *result) {
//set a break point here
int dataCount = result.count;
XCTAssert(0 == dataCount || 16 == dataCount, #"should have 0 or 16 items");
}];
}

Answer 1

In that case, because that is an asynchronous operation, the test is completing before the completion handler is called. With that in mind, there are two methods you can use to do this, both involving essentially waiting for the completion handler to be called before allowing your tests to complete.
The first method utilizes new APIs available in the Xcode 6 beta.
Method #1 - New XCTestExpectation APIs
- (void)testThatRequestSuperDecisionDataShouldReturnZeroOr14Items {
// set an expectation for your test, in this case we expect the completion handler to be
// called within a reasonable amount of time
XCTestExpectation *expectation = [self expectationWithDescription:#"The completion handler should be called."];
// start whatever asyncronous task you want to do
[_requestManager requestSuperDecisionDataWithCompletionHandler:^(NSArray *result) {
// here we handle the actual meat of the tests
int dataCount = result.count;
XCTAssert(0 == dataCount || 16 == dataCount, #"should have 0 or 16 items");
// now we can tell the test that our expectation has been fulfilled, which will
// allow the test to complete
[expectation fulfill];
}];
// we want the test to wait for the expectations for some period of time, but we also
// want to establish some sort of timeout interval where the test will basically be
// terminated and the result will be a timeout failure, you can set the timeout to whatever
// interval you want for each case, and optionally provide a handler to clean up anything
[self waitForExpectationsWithTimeout:2 handler:nil];
}
A second option is available if you are running Xcode 5 and thus don't have access to the new APIs, but is essentially the same process, just slightly more involved.
Method #2 - Do-it-yourself Async Testing
- (void)testThatRequestSuperDecisionDataShouldReturnZeroOr14Items {
// create a BOOL flag that will keep track of whether or not we're still
// waiting for the completion block to be called
__block BOOL waitingForBlock = YES;
// start whatever asyncronous task you want to do
[_requestManager requestSuperDecisionDataWithCompletionHandler:^(NSArray *result) {
// here we handle the actual meat of the tests
int dataCount = result.count;
XCTAssert(0 == dataCount || 16 == dataCount, #"should have 0 or 16 items");
// now we can update the waitingForBlock variable to NO as we are no
// longer waiting for it to complete
waitingForBlock = NO;
}];
// kill the test after some specified delay if we haven't completed yet - just in case something
// happens with the test where the handler will never be called, at least the test will complete
// and we will know we timed-out.
NSTimeInterval seconds = 3;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC), dispatch_get_main_queue(), ^(void) {
XCTFail(#"'testThatRequestSuperDecisionDataShouldReturnZeroOr14Items' failed due to timeout.");
waitingForBlock = NO;
});
// loop while we are waiting for the completion handler to finish
while (waitingForBlock) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
}
}