Writing an Avocado plugin

What better way to understand how an Avocado plugin works than creating one? Let’s use another old time favorite for that, the “Print hello world” theme.

Code example

Let’s say you want to write a plugin that adds a new subcommand to the test runner, hello. This is how you’d do it:

from avocado.core.output import LOG_JOB
from avocado.core.plugin_interfaces import CLICmd

class HelloWorld(CLICmd):

    name = 'hello'
    description = 'The classical Hello World! plugin example.'

    def run(self, args):

As you can see, this plugins inherits from avocado.core.plugin_interfaces.CLICmd. This specific base class allows for the creation of new commands for the Avocado CLI tool. The only mandatory method to be implemented is run and it’s the plugin main entry point.

This plugin uses avocado.core.output.LOG_JOB to produce the hello world output in the Job log. One can also use avocado.core.output.LOG_UI to produce output in the human readable output.

Registering Plugins

Avocado makes use of the setuptools and its entry points to register and find Python objects. So, to make your new plugin visible to Avocado, you need to add to your setuptools based setup.py file something like:

   'avocado.plugins.cli': [
      'hello = mypluginpack.hello:HelloWorld',

Then, by running either $ python setup.py install or $ python setup.py develop your plugin should be visible to Avocado.


The plugin registry mentioned earlier, (setuptools and its entry points) is global to a given Python installation. Avocado uses the namespace prefix avocado.plugins. to avoid name clashes with other software. Now, inside Avocado itself, there’s no need keep using the avocado.plugins. prefix.

Take for instance, the Job Pre/Post plugins are defined on setup.py:

'avocado.plugins.job.prepost': [
   'jobscripts = avocado.plugins.jobscripts:JobScripts'

The setuptools entry point namespace is composed of the mentioned prefix avocado.plugins., which is is then followed by the Avocado plugin type, in this case, job.prepost.

Inside Avocado itself, the fully qualified name for a plugin is the plugin type, such as job.prepost concatenated to the name used in the entry point definition itself, in this case, jobscripts.

To summarize, still using the same example, the fully qualified Avocado plugin name is going to be job.prepost.jobscripts.