test.m

- (void)testSetUserAsSuperuser
{	
        // set shared mock:
        [GHTestCase setSharedMock:[OCMockObject niceMockForClass:[NSUserDefaults class]]];
	
        // set expectations on shared mock:
	[[[GHTestCase sharedMock] expect] 
                                 setBool:YES 
                                  forKey:[OCMArg checkWithSelector:@selector(isEqualToString:) onObject:@"superuser"]]];
	
	// Swizzle in the mock
	[self swizzle:[NSUserDefaults class] selector:@selector(standardUserDefaults)];
	
                // run implementation
		[viewController setUserAsSuperuser];
                // verify shared mock
		GHAssertNoThrow([[GHTestCase sharedMock] verify], @"ViewController did not set user as superuser.");

	// DeSwizzle
	[self deswizzle];
}

#pragma mark -
#pragma mark Swizzleable Methods
	 
- (NSUserDefaults *)standardUserDefaults
{	
	return [GHTestCase sharedMock];
}

viewController.m

-(void) setUserAsSuperuser
{
  [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"superuser"];
}