testing

Git bisect is a git command that makes it easier to track down where a problem was introduced to a codebase.

In large projects you may find that a change was added to the code that causes a problem and you then need to track down where that problem occurred. Knowing where the problem was introduced makes debugging the issue a lot easier.

You could just checkout commits until you find the culprit, but git comes with the bisect tool that can assist in this process and can even be automated to quickly find the problem.

Performing behavioural testing on a Drupal project allows you to make sure that all of your features work as they should do. This is especially important when you update code as this can introduce bugs that are otherwise time consuming or difficult to spot.

One aspect that is important to behavioural tests is the content of the site, which is often integral to many Drupal sites functioning correctly. Many Drupal sites have taxonomy terms that are used in views to filter content in one way or another.

There are also structure pages that are used as signposts to other parts of the site, and they are often important in navigation. Whilst you could just visit the pages directly, it's often useful to test the user journey end-to-end, which involves being able to navigate to the functionality being tested.

Nightwatch.js is an end to end testing framework, written in JavaScript. It can be used to test websites and applications and uses the W3C WebDriver API to drive modern browsers to perform the tests.

In this article I will look at setting up Nightwatch.js in a project and getting started with writing tests.

Installing Nightwatch.js

To install Nightwatch.js you should have a npm project. This can be an existing project, but Nightwatch.js can be easily installed as a standalone application; which is useful if you just want to get familiar with the system.

Creating a new, empty, npm project can be done with the following command.

npm init -y

You can now include Nightwatch.js as a development dependency into your project.

npm install nightwatch --save-dev

I was talking with a fellow programmer the other day about a poor test that we were reviewing and we got onto the subject of what makes a poor test. The test in question had a reliance on a previous test being run, and the problem we encountered was that on some systems the dependent test was run after this test, which caused it to fail.

This also caused some headaches in local development as it couldn't be run in isolation. We had to ensure that both tests were run, in the correct order.

After fixing the tests so that they could be run independently I created a list of some common problems that programmers might come across when writing tests. These rules can be applied to most coding test, not just unit tests or behavioural tests.

Although Drupal SimpleTest is an extremely useful module it doesn't currently support data providers, which is a shame as I use that feature quite a bit in other testing frameworks. A data provider is a mechanism that allows you to call a single test case multiple times with different arguments so that you can ensure the correct output each time. This is useful because testing a single function once is fine, but testing it with a variety of different values can otherwise mean having multiple test cases.

To mimic this functionality in Drupal SimpleTest you can create a data provider method that returns an array, which is then used to test a particular function.

For example, let's say I have the following (trivial) function in a Drupal module.