Because I always forget.
id mockView = OCMClassMock([UIView class]);
[[[[mockView stub] ignoringNonObjectArgs] andDo:^(NSInvocation *invocation) {
__block void (^animationBlock)(void);
[invocation getArgument:&animationBlock atIndex:3];
animationBlock();
__block void (^completionBlock)(BOOL);
[invocation getArgument:&completionBlock atIndex:4];
completionBlock(YES);
}] animateWithDuration:0 animations:OCMOCK_ANY completion:OCMOCK_ANY];