iOS OCMock partial vs class mock

ios, ocmock

Solution

`Class mocks` create objects that are pure mocks of a class instance.

`Partial mocks` take an instance of a class an allow you to stub any of its methods.

Suppose I have these classes:

@interface Foo : NSObject
- (void)doX;
@end
@implementation
- (void)doX
{
    NSLog(@"X");
}
@end

@interface Bar : NSObject
- (void)doA:(Foo *)foo;
- (void)doB;
@end
@implementation Bar
- (void)doA:(Foo *)foo
{
    NSLog(@"A");
    [foo doX];
    [self doB];
}
- (void)doB
{
    NSLog(@"B");
}
@end

I'm interested in testing Bar's `doA:` method. I expect it to call `doX` on a `Foo` object, then to call its own `doB` method. I would implement this using a class mock of a Foo and a partial mock of a Bar.

- (void)test_doA_shouldCall_doX_and_doB
{
    id objectUnderTest = [OCMockObject partialMockForObject:[Bar new]];
    id fooMock = [OCMockObject mockForClass:Foo.class];
    [[fooMock expect] doX];
    [[objectUnderTest expect] doB];
    // Make the call
    [objectUnderTest doA:fooMock];
    [objectUnderTest verify];
    [fooMock verify];
}

You see here that my partial mock allowed me to call the real method I wanted to test while mocking an internal call to another of its instance methods. Because I didn't need any of the real functionality of Foo, however, I used a class mock.

Problem

Original source