Retain cycle unit tests

block_arg_cycles.m

@interface WMFRetainCycleTests : XCTestCase
@property (strong, nonatomic) void(^block)(id);
@end

@implementation WMFRetainCycleTests

- (void)testUsingArgument {
    WMFRetainCycleTests* noCycle = [WMFRetainCycleTests new];
    __weak WMFRetainCycleTests* weakRef = noCycle;
    noCycle.block = ^ (id y) {
        NSLog([y description]);
    };
    noCycle.block(noCycle); //< call block with itself
    noCycle = nil; //< nil out strong reference
    XCTAssertNil(weakRef); //< weak reference is nil! ✅
}

- (void)testReferencingCycle {
    WMFRetainCycleTests* cycle = [WMFRetainCycleTests new];
    __weak WMFRetainCycleTests* weakRef = cycle;
    cycle.block = ^ (id y) {
        NSLog([cycle description]); //< warning: captuing 'cycle' strongly in this block may create a retain cycle
    };
    cycle.block(cycle); //< try calling with itself for parity w/ previous test
    cycle = nil;
    XCTAssertNil(weakRef); //< failure! 🚨
}

@end