conftest.py

import time
import pytest

def pytest_configure_node(node):
    node.slaveinput['all_nodes'] = {'a': True, 'b': True, 'c': True}
    node.slaveinput['used_nodes'] = {}

def _get_browser(request):
    def get_browser():
        class Browser(object):
            node = None
        browser = Browser()
        if hasattr(request.config, 'slaveinput'):
            all_nodes = request.config.slaveinput['all_nodes']
            used_nodes = request.config.slaveinput['used_nodes']
            free_nodes = set(all_nodes.keys()) - set(used_nodes.keys())
            node = free_nodes.pop()
            used_nodes[node] = all_nodes[node]
            request.config.slaveinput['used_nodes'] = used_nodes
            browser.node = node
        return browser
    return get_browser

def _close_browser(request):
    def close_browser(browser):
        if hasattr(request.config, 'slaveinput'):
            used_nodes = request.config.slaveinput['used_nodes']
            del used_nodes[browser.node]
            request.config.slaveinput['used_nodes'] = used_nodes
    return close_browser

def pytest_funcarg__browser(request):
    return request.cached_setup(
             setup=_get_browser(request),
             teardown=_close_browser(request),
             scope='function')

output.txt

$ py.test test_hello.py -d --tx 2*popen//python=python
==================================================================== test session starts ====================================================================
platform linux2 -- Python 2.6.6 -- pytest-2.2.1
gw0 [4] / gw1 [4]
scheduling tests via LoadScheduling
FFFF
========================================================================= FAILURES ==========================================================================
_________________________________________________________________________ test_one __________________________________________________________________________
[gw1] linux2 -- Python 2.6.6 /home/baiju/ve/bin/python
browser = <conftest.Browser object at 0xb75f32cc>

    def test_one(browser):
        print browser.node
        time.sleep(.5)
>       assert browser.node == 1
E       assert 'a' == 1
E        +  where 'a' = <conftest.Browser object at 0xb75f32cc>.node

test_hello.py:6: AssertionError
---------------------------------------------------------------------- Captured stdout ----------------------------------------------------------------------
a
_________________________________________________________________________ test_two __________________________________________________________________________
[gw0] linux2 -- Python 2.6.6 /home/baiju/ve/bin/python
browser = <conftest.Browser object at 0xb744d2cc>

    def test_two(browser):
        print browser.node
        time.sleep(1)
>       assert browser.node == 1
E       assert 'a' == 1
E        +  where 'a' = <conftest.Browser object at 0xb744d2cc>.node

test_hello.py:11: AssertionError
---------------------------------------------------------------------- Captured stdout ----------------------------------------------------------------------
a
________________________________________________________________________ test_three _________________________________________________________________________
[gw1] linux2 -- Python 2.6.6 /home/baiju/ve/bin/python
browser = <conftest.Browser object at 0x9ccdd0c>

    def test_three(browser):
        print browser.node
        time.sleep(1.5)
>       assert browser.node == 1
E       assert 'a' == 1
E        +  where 'a' = <conftest.Browser object at 0x9ccdd0c>.node

test_hello.py:16: AssertionError
---------------------------------------------------------------------- Captured stdout ----------------------------------------------------------------------
a
_________________________________________________________________________ test_four _________________________________________________________________________
[gw0] linux2 -- Python 2.6.6 /home/baiju/ve/bin/python
browser = <conftest.Browser object at 0xa0afb4c>

    def test_four(browser):
        print browser.node
        time.sleep(1.3)
>       assert browser.node == 1
E       assert 'a' == 1
E        +  where 'a' = <conftest.Browser object at 0xa0afb4c>.node

test_hello.py:21: AssertionError
---------------------------------------------------------------------- Captured stdout ----------------------------------------------------------------------
a
================================================================= 4 failed in 2.67 seconds ==================================================================
(ve)

test_hello.py

import time

def test_one(browser):
    print browser.node
    time.sleep(.5)
    assert browser.node == 1

def test_two(browser):
    print browser.node
    time.sleep(1)
    assert browser.node == 1

def test_three(browser):
    print browser.node
    time.sleep(1.5)
    assert browser.node == 1

def test_four(browser):
    print browser.node
    time.sleep(1.3)
    assert browser.node == 1