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.
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:
../../../../../examples/plugins/cli-cmd/hello/hello.py
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
<avocado.core.plugin_interfaces.CLICmd.run>
and it's the plugin main entry point.
This plugin uses :pyavocado.core.output.LOG_UI
to produce the hello world output in the console.
Note
Different loggers can be used in other contexts and for different purposes. One such example is :pyavocado.core.output.LOG_JOB
, which can be used to output to job log files when running a job.
It is usual for a plugin to allow users to do some degree of configuration based on command-line options and/or configuration options. A plugin might change its behavior depending on a specific configuration option.
Frequently, those settings come from configuration files and, sometimes, from the command-line arguments. Like in most UNIX-like tools, command-line options will override values defined inside the configuration files.
You, as a plugin writer, don’t need to handle this configuration by yourself. Avocado provides a common API that can be used by plugins in order to register options and get values.
If your plugin has options available to the users, register it using the .Settings.register_option()
method during your plugin configuration stage. The options are parsed and provided to the plugin as a config dictionary.
Let’s take our Hello World example and change the message based on a “message” option:
../../../../../examples/plugins/cli-cmd/hello_option/hello_option.py
The code in the example above registers a configuration namespace (hello.message) inside the configuration file only. A namespace is a section (hello) followed by a key (message). In other words, the following entry in your configuration file is also valid and will be parsed:
[hello]
message = My custom message
As you can see in the example above, you need to set a default value and this value will be used if the option is not present in the configuration file. This means that you can have a very small configuration file or even an empty one.
This is a very basic example of how to configure options inside your plugin.
Now, let’s say you would like to also allow this change via the command-line option of your plugin (if your plugin is a command-line plugin). You need to register in any case and use the same method to connect your option namespace with your command-line option.
../../../../../examples/plugins/cli-cmd/hello_parser/hello_parser.py
Note
Keep in mind that not all options should have a “command-line” option. Try to keep the command-line as clean as possible. We use command-line only for options that constantly need to change and when editing the configuration file is not handy.
For more information about how this registration process works, visit the .Settings.register_option()
method documentation.
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:
../../../../../examples/plugins/cli-cmd/hello/setup.py
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 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
.
Plugins can extend the list of config files parsed by Settings
objects by dropping the individual config files into /etc/avocado/conf.d
(linux/posix-way) or they can take advantages of the Python entry point using avocado.plugins.settings
.
- `/etc/avocado/conf.d`:
In order to not disturb the main Avocado config file, those plugins, if they wish so, may install additional config files to /etc/avocado/conf.d/[pluginname].conf
, that will be parsed after the system wide config file. Users can override those values as well at the local config file level. Considering the config for the hypothethical plugin salad
:
[salad.core]
base = caesar
dressing = caesar
If you want, you may change dressing
in your config file by simply adding a [salad.core]
new section in your local config file, and set a different value for dressing
there.
- `avocado.plugins.settings`:
This entry-point uses avocado.core.plugin_interfaces.Settings
-like object to extend the list of parsed files. It only accepts individual files, but you can use something like glob.glob("*.conf")
to add all config files inside a directory.
You need to create the plugin (eg. my_plugin/settings.py
):
from avocado.core.plugin_interfaces import Settings
class MyPluginSettings(Settings):
def adjust_settings_paths(self, paths):
paths.extend(glob.glob("/etc/my_plugin/conf.d/*.conf"))
And register it in your setup.py
entry-points:
from setuptools import setup
...
setup(name="my-plugin",
entry_points={
'avocado.plugins.settings': [
"my-plugin-settings = my_plugin.settings.MyPluginSettings",
],
...
Which extends the list of files to be parsed by settings object. Note this has to be executed early in the code so try to keep the required deps minimal (for example the avocado.core.settings.settings is not yet available).
Avocado lets plugin developers to define plugin priority, which ensures the default execution order.The plugins with higher priority will be executed earlier than the plugins with lower priority. The priorities are on the scale between 0-100 and as default all plugins have priority set to NORMAL (50). For easier usage, avocado has predefined values in:
avocado.core.extension_manager.PluginPriority
To define a priority for plugin, you have to create class attribute priority
same as you're defining name
and description
:
../../../../../examples/plugins/cli-cmd/hello_priority/hello_priority.py
Now, the plugin HelloWorld
has priority high and will be executed before every plugin without priority variable (default priority).
As a plugin developer, you have to consider that users can change the execution order by plugins.$type.order
option. In such case, at first will be executed the plugins from plugins.$type.order
and then the rest of plugins by its priority. For example the default order is [plugin1, plugin2, plugin3, plugin4] the plugins.$type.order
is [plugin2, plugin4] then the real order will be [plugin2, plugin4, plugin1, plugin3]
For a new test type to be recognized and executed by Avocado's NRunner architecture, there needs to be two types of plugins and one optional:
- resolvers: they resolve references into proper test descriptions that Avocado can run.
- discoverers (optional): They are doing the same job as resolvers but without a reference. They are used when the tests can be created from different data e.g. config files.
- runners: these make use of the resolutions made by resolvers and actually execute the tests, reporting the results back to Avocado
The following example shows real code for a resolver and a runner for a magic test type. This magic test simply passes or fails depending on the test reference.
The resolver implementation will simply set the test type (magic) and transform the reference given into its url:
../../../../../examples/plugins/tests/magic/avocado_magic/resolver.py
The runner will receive the avocado.core.nrunner.runnable.Runnable
information created by the resolver plugin. Runners can be written in any language, but this implementation reuses some base Python classes.
First, avocado.core.nrunner.runner.BaseRunner
is used to write the runner class. And second, the avocado.core.nrunner.app.BaseRunnerApp
is used to create the command line application, which uses the previously implemented runner class for magic
test types.
../../../../../examples/plugins/tests/magic/avocado_magic/runner.py
A runner is free to make use of all the information in the avocado.core.nrunner.runnable.Runnable
that the resolver implementation populates. In this particular example it only makes use of the uri <avocado.core.nrunner.runnable.Runnable.uri>
attribute. If a runner needs to behave accordingly to some Avocado configuration, you need to declare that configuration in the CONFIGURATION_USED
<avocado.core.nrunner.runner.BaseRunner.CONFIGURATION_USED>
class attribute and then you can access it in config
<avocado.core.nrunner.runnable.Runnable.config>
.
The plugins need to be registered so that Avocado knows about it. See registering-plugins
for more information. This is the code that can be used to register these plugins:
../../../../../examples/plugins/tests/magic/setup.py
With that, you need to either run python setup.py install
or python setup.py develop
.
Note
The last entry, registering a console_script
, is recommended because it allows one to experiment with the runner as a command line application (avocado-runner-magic
in this case). Also, depending on the spawner implementation used to run the tests, having a runner that can be executed as an application (and not a Python class) is a requirement.
With the plugins activated, you should be able to run avocado plugins
and find (among other output):
Plugins that resolve test references (resolver):
...
magic Test resolver for magic words
...
Resolving the "pass" and "fail" references that the magic plugin knows about can be seen by running avocado list pass fail
:
magic pass
magic fail
And you may get more insight into the resolution results, by adding a verbose parameter and another reference. Try running avocado -V list pass fail something-else
:
Type Test Tag(s)
magic pass
magic fail
Resolver Reference Info
avocado-instrumented pass File "pass" does not end with ".py"
exec-test pass File "pass" does not exist or is not a executable file
golang pass
avocado-instrumented fail File "fail" does not end with ".py"
exec-test fail File "fail" does not exist or is not a executable file
golang fail
avocado-instrumented something-else File "something-else" does not end with ".py"
exec-test something-else File "something-else" does not exist or is not a executable file
golang something-else
magic something-else Word "something-else" is not a valid magic word
python-unittest something-else File "something-else" does not end with ".py"
robot something-else File "something-else" does not end with ".robot"
tap something-else File "something-else" does not exist or is not a executable file
TEST TYPES SUMMARY
==================
magic: 2
It's worth realizing that magic (and other plugins) were asked to resolve the something-else
reference, but couldn't:
Resolver Reference Info
...
magic something-else Word "something-else" is not a valid magic word
...
The common way of running Avocado tests is to run them through avocado run
. To run both the pass
and fail
magic tests, you'd run avocado run -- pass fail
:
$ avocado run -- pass fail
JOB ID : 86fd45f8c1f2fe766c252eefbcac2704c2106db9
JOB LOG : $HOME/avocado/job-results/job-2021-02-05T12.43-86fd45f/job.log
(1/2) pass: STARTED
(1/2) pass: PASS (0.00 s)
(2/2) fail: STARTED
(2/2) fail: FAIL (0.00 s)
RESULTS : PASS 1 | ERROR 0 | FAIL 1 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB HTML : $HOME/avocado/job-results/job-2021-02-05T12.43-86fd45f/results.html
JOB TIME : 1.83 s