pytest-localserver 0.10.0

Quickstart

myproject.py

import requests


def make_request(url):
    """A function that makes a web request."""
    rsp = requests.get(url)
    return rsp.text

test_myproject.py

from myproject import request


def test_make_request(httpserver):
    httpserver.serve_content(
        content="success",
        code=200,
    )

    assert make_request(httpserver.url) == "success"

How-To

Let’s say you have a function to scrape HTML which only required to be pointed at a URL :

import requests

def scrape(url):
  html = requests.get(url).text
  # some parsing happens here
  # ...
  return result

You want to test this function in its entirety without having to rely on a remote server whose content you cannot control, neither do you want to waste time setting up a complex mechanism to mock or patch the underlying Python modules dealing with the actual HTTP request (of which there are more than one BTW). So what do you do?

You simply use pytest’s fixture feature and simulate an entire server locally!

def test_retrieve_some_content(httpserver):
    httpserver.serve_content(open("cached-content.html").read())
    assert scrape(httpserver.url) == "Found it!"

What happened here is that for the duration of your tests an HTTP server is started on a random port on localhost which will serve the content you tell it to and behaves just like the real thing.

The added bonus is that you can test whether your code behaves gracefully if there is a network problem:

def test_content_retrieval_fails_graciously(httpserver):
  httpserver.serve_content("File not found!", 404)
  pytest.raises(ContentNotFoundException, scrape, httpserver.url)

The same thing works for SMTP servers, too:

def test_sending_some_message(smtpserver):
    mailer = MyMailer(host=smtpserver.addr[0], port=smtpserver.addr[1])
    mailer.send(
        to="bob@example.com",
        from_="alice@example.com",
        subject="MyMailer v1.0",
        body="Check out my mailer!"
    )
    assert len(smtpserver.outbox)==1

Here an SMTP server is started which accepts e-mails being sent to it. The nice feature here is that you can actually check if the message was received and what was sent by looking into the smtpserver’s outbox.

It is really that easy!

Fixtures

Here is a short overview of the available pytest fixtures and their usage. This information is also available via pytest –fixtures. For more details I suggest poking around in the code itself.

httpserver

provides a threaded HTTP server instance running on localhost. It has the following attributes:

• code - HTTP response code (int)

• content - content of next response (str, bytes, or iterable of either)

• headers - response headers (dict)

• chunked - whether to chunk-encode the response (enumeration)

• store_request_data - whether to store request data for later use

Once these attributes are set, all subsequent requests will be answered with these values until they are changed or the server is stopped. A more convenient way to change these is :

httpserver.serve_content(
    content=None,
    code=200,
    headers=None,
    chunked=pytest_localserver.http.Chunked.NO,
    store_request_data=True
)

The chunked attribute or parameter can be set to

• Chunked.YES, telling the server to always apply chunk encoding

• Chunked.NO, telling the server to never apply chunk encoding

• Chunked.AUTO, telling the server to apply chunk encoding only if the Transfer-Encoding header includes chunked

If chunk encoding is applied, each str or bytes in content becomes one chunk in the response.

You can use store_request_data=False to disable loading the request data into memory. This will make it impossible to check the request data using httpserver.requests[index].data but may make sense when posting a larger amount of data and you don’t need to check this.

The server address can be found in property

• url

which is the string representation of tuple server_address (host as str, port as int).

If you want to check which form fields have been POSTed, Try

httpserver.serve_content(..., show_post_vars=True)

which will display them as parsable text.

If you need to inspect the requests sent to the server, a list of all received requests can be found in property

• requests

which is a list of werkzeug.wrappers.Request objects.

httpsserver

is the same as httpserver only with SSL encryption.

smtpserver

provides a threaded SMTP server, with an API similar to smtpd.SMTPServer, (the deprecated class from the Python standard library) running on localhost. It has the following attributes:

• addr - server address as tuple (host as str, port as int)

• outbox - list of email.message.Message instances received.

Using your a WSGI application as test server

As of version 0.3 you can now use a WSGI application to run on the test server :

import pytest
from pytest_localserver.http import WSGIServer

from myproject import make_request


def simple_app(environ, start_response):
    """Respond with success."""
    status = "200 OK"
    response_headers = [("Content-type", "text/plain")]
    start_response(status, response_headers)
    return ["success".encode("utf-8")]


@pytest.fixture
def testserver():
    """Server for simple_app."""
    server = WSGIServer(application=simple_app)
    server.start()
    yield server
    server.stop()


def test_make_request(testserver):
    """make_request() should return "success"."""
    assert make_request(testserver.url) == "success"

Have a look at the following page for more information on WSGI: http://wsgi.readthedocs.org/en/latest/learn.html

Download and Installation

You can install the plugin by running

pip install pytest-localserver

Alternatively, get the latest stable version from PyPI or the latest bleeding-edge from Github.

License and Credits

This plugin is released under the MIT license. You can find the full text of the license in the LICENSE file.

Copyright (C) 2010-2022 Sebastian Rahlf and others (see AUTHORS).

Some parts of this package is based on ideas or code from other people:

• I borrowed some implementation ideas for the httpserver from linkchecker.

• The implementation for the SMTP server is based on the Mailsink recipe by Adam Feuer, Matt Branthwaite and Troy Frever.

• The HTTPS implementation is based on work by Sebastien Martini.

Thanks guys!

Development and future plans

Feel free to clone the repository and add your own changes. Pull requests are always welcome!:

git clone https://github.com/pytest-dev/pytest-localserver

If you find any bugs, please file a report.

Test can be run with tox.

I already have a couple of ideas for future versions:

• support for FTP, SSH (maybe base all on twisted?)

• making the SMTP outbox as convenient to use as django.core.mail.outbox

• add your own here!