Use docstrings to list tests in py.test

Here is a simple test file:

# test_single.py
def test_addition():
    "Two plus two is still four"
    assert 2 + 2 == 4

def test_addition2():
    "One plus one is still two"
    assert 1 + 1 == 2

The default output in py.test is like

$ py.test test_single.py -v
[...]
test_single.py::test_addition PASSED
test_single.py::test_addition2 PASSED

I would like to have

Two plus two is still four PASSED
One plus one is still two PASSED

i.e. use the docstrings as descriptions for the tests.

I tried to use a customization in a conftest.py file:

import pytest

@pytest.mark.tryfirst
def pytest_runtest_makereport(item, call, __multicall__):
    # execute all other hooks to obtain the report object
    rep = __multicall__.execute()
    if rep.when == "call":
        extra = item._obj.__doc__.strip()
        rep.nodeid =  extra
    return rep

that is close, but it repeats the filename on every line:

$ py.test test_single.py
======================================================================================== test session starts =========================================================================================
platform darwin -- Python 2.7.7 -- py-1.4.26 -- pytest-2.6.4
plugins: greendots, osxnotify, pycharm
collected 2 items

test_single.py
And two plus two is still four .
test_single.py
And one plus one is still two .

====================================================================================== 2 passed in 0.11 seconds ======================================================================================

How can I avoid the lines with test_single.py in the output, or maybe print it only once?

Looking into the source of py.test and some of its plugins did not help.

I am aware of the pytest-spec plugin, but that uses the function's name as a description. I don't want to write def test_two_plus_two_is_four().