CODEWITHSUNDEEP
iosobjective-cunit-testingocmock
Leem.fin
Leem.fin

Reputation: 42602

stub method return doesn't work in unit test

I am using OCMock to do unit test.

I have a singleton class MyManager:

@implementation MyManager
+ (id)sharedManager {
    static MyManager *sharedMyManager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedMyManager = [[self alloc] init];
    });
    return sharedMyManager;
}

// This is the function I want to stub in my test case
- (NSInteger) getId{
  return [self askBackendToReturn];
}
...
@end

In my test case, I want to stub the return of -(NSInteger) getId:. I tired the following:

id mgrMock = OCMClassMock([MyManager class]);
// read OCMock 3 document, seems the return from OCMClassMock can be either a mocked class or mocked instance. The following line of code is according to its documents "Stubbing methods that create objects" http://ocmock.org/reference/#advanced-topics
OCMStub([[mgrMock alloc] init]).andReturn(mgrMock);

// Now I stub the function to return 1
OCMStub([mgrMock getId]).andReturn(1);

// test it, I still get the real id from backend, WHY?
MyManager *sharedManager = [MyManager sharedManager];
NSInteger mgrId = [sharedManager getId];

But when I run, the stub return is not working, it still return the real id. WHY?

Upvotes: 0

Views: 286

Answers (1)

Kyle Parent
Kyle Parent

Reputation: 460

The reason it's returning the real id is because once [self alloc] is called in your implementation, you are dealing with a new instance of MyManager. This means that in [[self alloc] init] you end up calling init on a brand new instance who has no knowledge of the stubbed methods.

If you want to take the approach of stubbing the MyManager initialization, you will have to stub both [mgrMock alloc] and [mgrMock init] to return your mock object.

In this spirit of unit testing, my suggestion is to nix this approach entirely, and instead simply stub sharedManager to return mgrMock. Your test is related to the singleton's Id, and should assume that initialization is working as expected.

Upvotes: 1

Related Questions