Strange retain cycle warning in unit tests in Xcode - ios

Question

I have a service that I'm currently writing a unit test for. The code works as expected, but I'm getting a strange retain cycle warning.
[self.myService doSomethingCoolWithCompletionBlock:^(MyResponseObject *obj) {
XCTAssertNil(obj, #"obj should be nil");
}];
The XCTAssertNil(obj, #"obj should be nil"); line shows a warning in Xcode Capturing 'self' strongly in this block is likely to lead to a retain cycle.
If I change the code to the following, the warning is removed:
__weak MyService *weakService = self.myService;
[weakService doSomethingCoolWithCompletionBlock:^(MyResponseObject *obj) {
XCTAssertNil(obj, #"obj should be nil");
}];
I am using self.someService in other unit tests, and never had this issue. Anyone experienced this before?
EDIT
I have another test that has the following:
[self.myService doSomethingElseCoolWithCompletionBlock:(NSArray *results) {
XCTestAssertNotNil(results, #"results should not be nil");
}];
This doesn't give me a warning. The only difference I see is that this is checking an array, and the other is checking an object of a specific type.

Answer 1

assert it is macros and used self inside.
so you need create local variable with name self.
__weak id weakSelf = self;
self.fooBlock = ^{
id self = weakSelf;
XCTAssert(YES);
};

Answer 2

Don't do this:
#interface MyCoolTests : XCTestCase
#property (retain) id myService;
#end
#implementation MyCoolTests
-(void)testCoolness{
self.myService = [MyService new];
self.myService.callback = ^{
XCTAssert(YES);
};
// ...
}
#end
Do this:
#interface MyCoolTests : XCTestCase
#end
#implementation MyCoolTests
-(void)testCoolness{
id myService = [MyService new];
myService.callback = ^{
XCTAssert(YES);
};
// ...
}
#end
It's a limitation of XCTTestCase and it probably catches people when using the setup method.