This chapter describes how to run various tests locally in a development environment, guidelines for writing tests, and information regarding the continuous testing infrastructure.

Running Tests Locally#

Before attempting to run Panel tests, make sure you have successfully run through all of the instructions in the Getting Set Up section of the Developer’s Guide.

Test Selection#

Currently Panel uses linting and two types of tests regular unit tests which are run with pytest and notebook example tests run with nbsmoke:

To run flake checking use:

doit test_flakes

To run unit tests use:

doit test_unit

To run example smoke tests use:

doit test_examples

Integration tests#

Writing Tests#

In order to help keep Panel maintainable, all Pull Requests that touch code should normally be accompanied by relevant tests. While exceptions may be made for specific circumstances, the default assumption should be that a Pull Request without tests may not be merged.

Python Unit Tests#

Python unit tests maintain the basic functionality of the Python portion of the Panel library. A few general guidelines will help you write Python unit tests:

absolute imports

In order to ensure that Panel’s unit tests as relocatable and unambiguous as possible, always prefer absolute imports in test files. When convenient, import and use the entire module under test:

  • GOOD: import panel.widgets

  • GOOD: from panel.layout import Column

  • BAD: from ..models.widgets import Player


All new tests should use and assume pytest for test running, fixtures, parameterized testing, etc. New tests should not use the unittest module of the Python standard library.

Continuous Integration#

Every push to the master branch or any Pull Request branch on GitHub automatically triggers a full test build on the GitHub Actions continuous integration service. This is most often useful for running the full Panel test suite continuously, but also triggers automated scripts for publishing releases when a tagged branch is pushed.

You can see the list of all current and previous builds at this URL: https://github.com/holoviz/panel/actions


There are a number of files that affect the build configuration:

  • .github/worksflows/test.yaml

    Defines the build matrix and global configurations for the stages described below.

  • conda.recipe/meta.yaml

    Instructions for building a conda noarch package for Panel.

  • setup.py

    Used to build sdist packages and “dev” installs. This file is the single source of truth of all dependencies.

  • tox.ini

    Contains the configuration for the doit commands .


GitHub Actions provides free build workers to Open Source projects. A few considerations will help you be considerate of others needing these limited resources:

  • Group commits into meaningful chunks of work before pushing to GitHub (i.e. don’t push on every commit).

  • If you must make multiple commits in succession, navigate to GitHub Actions and cancel all but the last build, in order to free up build workers.