Custom backends

Though tavern supports a few backends out of the box, you may want to extend it to support your own. This can be done by creating a new plugin that implements the necessary functionality and registers it with tavern.

First, write your backend and set up the request, response, etc as according to the standard plugin system. Note the standard restrictions - there can only be one ‘request’ per stage.

Entry Point Configuration¶

In your project’s pyproject.toml, configure the plugin entry point:

[project.entry-points.tavern_your_backend_name]
my_implementation = 'your.package.path:your_backend_module'

Then when running tests, specify the extra backend:

pytest --tavern-extra-backends=your_backend_name
# Or, to specify an implementation to override the project entrypoint:
pytest --tavern-extra-backends=your_backend_name=my_other_implementation

Or the equivalent in pyproject.toml or pytest.ini. Note:

• The entry point name should start with tavern_.

• The key of the entrypoint is just a name of the implementation and can be anything.

• The --tavern-extra-backends flag should not be prefixed with tavern_.

• If Tavern detects multiple entrypoints for a backend, it will raise an error. In this case, you must use the second form to specify which implementation of the backend to use. This is similar to the build-in --tavern-http-backend flag.

This is because Tavern by default only tries to load “grpc”, “http” and “mqtt” backends. The flag registers the custom backend with Tavern, which can then tell stevedore to load the plugin from the entrypoint.