Extending Elpy

Writing Modules

Modules are a way of easily extending Elpy with modular extensions. In essence, a module is a function which is called once to initialize itself globally, then once every time elpy-mode is enabled or disabled, and also once if elpy is disabled globally.

To achieve this, a module function receives one or more arguments, the first of which is the command specifier symbol, which can be one of the following:

Called once, when Elpy is enabled using elpy-enable.
Called once, when Elpy is disabled using elpy-disable.
Called in a buffer when elpy-mode is enabled.
Called in a buffer when elpy-mode is disabled.

To activate a module, the user has to add the function to elpy-modules.

Writing Test Runners

A test runner is a function that receives four arguments, described in the docstring of elpy-test-at-point. If only the first argument is given, the test runner should find tests under this directory and run them. If the others are given, the test runner should run the specified test only, or as few as it can.

Test runners should use an interactive spec of (interactive (elpy-test-at-point)) so they can be called directly by the user. For their main work, they can use the helper function elpy-test-run. See the elpy-test-discover-runner for an example.

To make it possible to set the test runner as a file-, directory- or project-local variable, the function symbol should get the elpy-test-runner property with a value of t.

Running Tests:

You can set up a working environment for Elpy using pip and cask. After installing Cask, create a new virtual environment and run the setup script in it:

virtualenv ~/.virtualenvs/elpy
source ~/.virtualenvs/elpy/bin/activate

You can now run ./scripts/test to run Elpy’s test suite.

If you cannot (or do not want to) use virtual environments on your system, you can set the environment variable ELPY_TEST_DONT_USE_VIRTUALENV to skip tests involving virtual environments: ELPY_TEST_DONT_USE_VIRTUALENV=t ./scripts/test.