mock patch not work with nosetests

I just tried to learn the mock and nosetests by running simple examples, but got no luck:

john$ nosetests test_mylib.py
E
======================================================================
ERROR: test_mylib.test_mylib_foo
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/wjq/py-virtenv-2.7.5/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/Users/wjq/py-virtenv-2.7.5/lib/python2.7/site-packages/mock.py", line 1201, in patched
    return func(*args, **keywargs)
TypeError: test_mylib_foo() takes exactly 2 arguments (1 given)

However if I run the test directly, it's ok:

john$ python test_mylib.py
john$ 

I think I must miss some key understanding on the tow libraries since I'm new to them. Really appreciate if someone can point them out.

The followings are my example codes.

test_mylib.py

import mock
import mylib

@mock.patch('mylib.incr')
def test_mylib_foo(aa, incr):
    incr.return_value=5
    assert mylib.foo(1) == 6

if __name__ == '__main__':
    test_mylib_foo(123)

mylib.py

from depen import incr
def foo(aa):
    return incr(aa) +1

depen.py

def incr(aa):
    return aa+1