When it comes to unit testing tools that fetch HTTP resources, we decided we'd like to have a way to easily store pre-determined responses, and then serve them from a server in the same process as we're running these tests. No monkey patching, no infrastructure (like a caching proxy server).
It should be mentioned that if you're looking to capture requests from existing services and then replay them, the vcr project has been ported to several languages and is very useful.
Twisted comes with a feature called
as-is serving, inspired by Apache. But,
who wants to include Twisted as a dependency?
This is based on
bottle, and thus supports a number of WSGI backends
(including Twisted and gevent), and is meant to be lightweight. An
document is one in which both the headers and the content for an HTTP response
HTTP/1.0 200 OK Content-Length: 137 Content-Type: text/html <html> <head> <title>Basic Test Page</title> </head> <body> <p>Hello, I'm a test page</p> </body> </html>
Note that this requires only newlines for the headers -- the carriage returns are added automatically for convenience.
sudo pip install asis
Or for those who prefer from source:
git clone https://github.com/seomoz/asis cd asis && sudo python setup.py install
You can run an
asis server relatively easily:
import asis # Serve files stored in 'foo/' on port 8080 server = asis.Server('foo', 8080) server.run() ... server.stop()
Alternatively, it can be used in a context-manager fashion:
import asis import requests with asis.Server('foo') as server: requests.get('http://localhost:8080/foo/bar.asis')
There's also a command-line utility included for convenience for serving asis
files as a standalone server, which is especially helpful for seeing these
curl or the browser:
# Serve files out of 'foo/' on port 8080 asis-server foo --port 8080 # Same, using gevent and being verbose asis-server foo --port 8080 --server gevent --verbose
Bells and Whistles
There are few features you may need to take advantage of:
If you supply the
Content-Encoding header as either
plain contents stored in the file are compressed and sent over the wire that
way. In those cases, you can leave
Content-Length as 0, and the true content
length (after compression) will be sent in its place. For example, the
following gets sent as gzip-compressed content correctly to the browser:
HTTP/1.0 200 OK Content-Length: 0 Content-Type: text/plain Content-Encoding: gzip Hello world!
If you include a
charset in your
Content-Type header, then your content
will be interpreted as
utf-8 on disk, and then encoded in the provided
encoding. The idea is to help the editing process so that you don't have to
explicitly save your examples in their declared character set. Like changes to
Content-Length header is recomputed to be correct
once the transformation is complete.
Directives provided under the 'Asis' header are stripped out of the document
before being sent along, and can offer ways of modifying default behavior. The
directives can be
;-separated, and currently include:
no-header-encode-- Don't encode change the encoding of headers. They're supposed to be
iso-8859-1, but sometimes this is part of the beahvior you're trying to test
no-charset-- Don't encode the output in the provided charset and instead leave it as is
no-encoding-- Don't encode the output in the provided encoding (
deflate, etc.) and just leave it as is
By default, the server is started with the
gevent server, and it's started in
a background green thread, and it supposed to be ready to serve requests as
Alternatively, the server can be started in two other modes,
fork, then it will run the server in a separate process, and it
still works as both a context manager and after calling
selected, then it runs in a blocking way. For example:
# Run it in a separate process with asis.Server('foo', port=8080, mode='fork'): # Make some requests ...
Examples and Tests
Included in here are a number of examples of as-is documents, and
be run directly to verify that they are transferred correctly:
It also provides an example of how you might incorporate it into your unit tests
Questions, comments, ideas always welcome.