Edit-Plackup-Test-Rinse-Repeat
At INOC, my place of work, I work on a lot of web applications with the backend written in Perl using Catalyst, and the frontend written in Javascript using ExtJS. With a UI written completely in Javascript, I often encounter bugs of the following form:
- Fire up Catalyst.
- Login.
- Click through half a dozen controls in the UI.
- Enter some data.
- Click “submit”.
- Watch the web application give you an angry error.
As you can imagine, the time for a single iteration of this cycle is fairly long, and the process is quite tedious. Obviously, if the error lies within the Javascript side, there's not much I can do about it, short of writing a Greasemonkey script to do some of the automation for me. However, half of the time, the server is returning some strange output given a certain set of inputs for a particular RPC call. Wouldn't it be nice if you could go through the application and have it record the requests you make to be submitted over and over again at a later time?
That's why I wrote Plack-Middleware-Recorder.
Plack-Middleware-Recorder is a distribution that comes with several modules:
- Plack::Middleware::Recorder
- A PSGI middleware that knows how to serialize requests to a stream.
- Plack::Middleware::Debug::Recorder
- A debugging panel that allows you to manipulate the recorder middleware from a browser.
- Plack::VCR
- A utility module that allows you to read a recorded request stream.
These modules allow you to build PSGI applications and scripts that record and replay requests to a web application. However, Plack-Middleware-Recorder also contains two scripts, plack-record and plack-replay, that do exactly what they sound like. So my workflow for handling a server-side bug goes from this:
- Steps 1 - 6 above
- Add some debugging log output
- Repeat, and observe the new output
to this:
- plack-record > requests.out
- Steps 1 - 6
- Add some debugging log output
- plack-replay requests.out app.psgi
- GOTO 3
Plack-Middleware-Recorder is still very young; I plan on adding better session support, dumping request streams to test files, and other features in the future. In the week since I've written it, I've already gotten a lot of mileage out of it; I hope other people find it just as useful!
-Rob
(cross-posted from my blog)
I'm a Perl programmer from Wisconsin.
https://hoelz.ro
This looks awesome, but have you tried Selenium? It has Perl bindings and can test that the JavaScript works as expected.
I would second preaction, take a look at Selenium to drive your browser.
preaction, Leo, thanks for your suggestion! I actually tried Selenium a couple of weeks ago; it's very nice, but unfortunately it doesn't play very well with ExtJS. ExtJS assigns HTML ids to every element it generates, and you can't really rely on them being the same every time. As far as I can tell, Selenium relies on consistent element IDs to do its job. It seemed to me that to get it working with ExtJS, I would have to heavily modify the scripts that Selenium generates, which would be more work than what I do with Plack::Middleware::Recorder.