Recently I found myself wondering how I was going to test my new GopherJS gRPC-Web bindings. Writing tests was something I had been waiting with until I had something working, mostly because I had no idea how I was going to meaningfully test GopherJS code that relies on interactions with JS and the reponses of a server.
I have in the past made a small contribution to the GopherJS websocket repo, and found myself impressed with the extensive tests written for the repo. It uses QUnit and the GopherJS QUnit bindings. Unfortunately it appears it the bindings were written for QUnit 1.5, which is quite old, but it does fine for a basic unit testing framework.
The journey starts
I sat about writing some QUnit tests and found the experience pretty spartan but good enough for my purposes. After writing some tests and wiring up the GopherJS client to be hosted by my server, navigating to the hosted page gives you a screen that looks like this:
Yay all tests pass! We could leave it here and just tell ourselves that we’ll run the tests every time we add something, no problem. But I was still not happy that this required a manual step every time we wanted to verify the code. I wanted to find some way to automate the step that is currently manual, that is, navigate to the page and check that there are no errors.
I’ve had dealings with various WebDrivers before, but I hadn’t yet had to solve the problem of parsing a web page in a Go context. I had seen Agouti in passing before when browsing the official web page of the test framework we use at work - Ginkgo. Here was a Ginkgo compatible test framework that could solve my problem! I of course jumped at the chance to try it.
Working with Agouti is simple if you’ve ever used a WebDriver before,
all the usual
FindByX are there, and it’s also got cool Gomega matchers
BeFound(). All I needed to do was write the code
to open the browser to
https://localhost:10000 where my QUnit tests
were being hosted by the server, then do a little bit of parsing of the
page to find out whether any tests had failed, and then fail the Agouti
test based on that.
I also spent a little time on writing out the errors produced by QUnit for a couple of different error types so that I would get a more helpful message than just “Tests failed!” if there was a test failure.
I ended up with a test suite that starts the server hosting the GopherJS,
spins up a chrome browser window via
chromedriver, navigates to the page,
grabs the JS rendered DOM content, parses parts of it to see whether any tests failed,
and reports the result. All now done via one single command.
Of course - the best part about this is that Agouti can be made to run with any WebDriver compatible browser client, so Selenium, PhantomJS etc can be plugged in in place of chromedriver. Free compatibility testing!
I’ve introduced the GopherJS QUnit bindings and Agouti, two packages that make it a breeze to confidently test your GopherJS packages. The source for all this is available on my github, feel free to take a look!
If you enjoyed this blog post, have any questions or input,
don’t hesitate to contact me on
jbrandhorst on the Gophers Slack. I’d love to hear