You can stub the class method "devices" to return an array with the contents of your choosing.
id deviceMock = [OCMockObject niceMockForClass:[AVCaptureDevice class]];
// I think you need to change your return value code to this for the booleans:
[[[deviceMock stub] andReturnValue:OCMOCK_VALUE((BOOL){YES})] hasMediaType:AVMediaTypeVideo];
[[[deviceMock stub] andReturnValue:OCMOCK_VALUE((BOOL){YES})] isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus];
[[[deviceMock stub] andReturnValue:OCMOCK_VALUE((BOOL){YES})] lockForConfiguration:nil];
// No need to wrap the position in an NSNumber
[(AVCaptureDevice*)[[deviceMock stub] andReturnValue:AVCaptureDevicePositionBack] position];
// Stub the class method that returns the devices array
[[[deviceMock stub] andReturn:@[ deviceMock ]] devices];
[[deviceMock expect] setFocusPointOfInterest:CGPointZero];
[[deviceMock expect] setFocusMode:AVCaptureFocusModeAutoFocus];
[[deviceMock expect] unlockForConfiguration];
[self waitForCompletion:0.55]; //Wait for UI animation
[deviceMock verify]
I think that should get you on your way.