using wsgiref.simple_server in unittests

Question

I has some function like this one:

URL = 'http://localhost:8080'
def func():
    response = urlopen(URL)
    return process(response)

And i want to test it with unittest. I do something like this:

from wsgiref.simple_server import make_server
def app_200_hello(environ,start_response):
    stdout = StringIO('Hello world')
    start_response("200 OK", [('Content-Type','text/plain')])
    return [stdout.getvalue()]

s = make_server('localhost', 8080, app_200_hello)

class TestFunc(unittest.TestCase):
    def setUp(self):
        s.handle_request()

    def test1(self):
        r = func()
        assert r, something

if __name__ == '__main__':
    unittest.main()

At setUp() my tests are stoping because s.handle_request() wait for request. How i can go around that? Run s.handle_request() in another thread? or maybe there is another solutions?

EDIT: I want to test "func" function, not "app_200_hello"

Answer 1

If you are testing a WSGI application, I can strongly recommend werkzeug.test which gets around these issues by testing the application itself without a server:

from werkzeug.test import Client

# then in your test case
def test1(self):
    client = Client(app_200_hello)
    appiter, status, headers = client.open()
    assert ''.join(appiter) == 'Hello World'
    assert status == '200 OK'

This approach just removes the need for a WSGI server altogether.

Of course if you did want to start a server, you would have to use a separate thread or a process, but then you have to make sure you stop it afterwards. However, it strikes me that the only time you would want to test with a real server is for production integration testing, in which case your server won't be wsgiref, it will be a real server that you probably won't have to start-stop like this.

Answer 2

Your server must be a separate process.

You'll want to start it with subprocess.Popen()

If you're using Python 2.6, you can then kill the subprocess during tearDown.

def setUp( self ):
    self.server= subprocess.Popen( "python","myserver","etc." )
def tearDown( self ):
    self.server.kill()

If you're not using Python 2.6, killing the server can be unpleasant.

Answer 3

My solution:

URL = 'http://localhost:8085'
def func():
    response = urlopen(URL)
    return response.read()

import unittest
from wsgiref.simple_server import WSGIServer, WSGIRequestHandler
import threading
from urllib2 import urlopen
from cStringIO import StringIO

def app_200_hello(environ,start_response):
    stdout = StringIO('Hello world')
    start_response("200 OK", [('Content-Type','text/plain')])
    return [stdout.getvalue()]

server = WSGIServer(('localhost', 8085), WSGIRequestHandler)
server.set_app(app_200_hello)

t = threading.Thread(target=server.serve_forever)
t.start()

class TestFunc(unittest.TestCase):
    def setUp(self):
        pass

    def test1(self):
        r = func()
        self.assertEqual(r, 'Hello world')

    def __del__(self):
        server.shutdown()

if __name__ == '__main__':
    unittest.main()

I start "server" in another thread and shutdown it at TestFunc destructor.

Answer 4

You could also provide a mock version of urlopen that doesn't actually run the server.

Assuming your original code was in mycode.py, in your test code you'd do something like:

import mycode

class TestFunc(unittest.TestCase):
    def setUp(self):
        # patch mycode, to use mock version of urlopen
        self._original_urlopen = mycode.urlopen
        mycode.urlopen=self.mock_urlopen

    def tearDown(self):
        # unpatch urlopen
        mycode.urlopen=self._original_urlopen

    def mock_urlopen(self,url):
        # return whatever data you need urlopen to return

    def test1(self):
        r = func()
        assert r, something

if __name__ == '__main__':
    unittest.main()

This is known as "monkey patching" which some frown upon, but for testing your code it can make life a lot easier, as you don't need to change your original code to make it testable.