# Testing JupyterHub¶

Unit test help validate that JupyterHub works the way we think it does, and continues to do so when changes occur. They also help communicate precisely what we expect our code to do.

JupyterHub uses pytest for all our tests. You can find them under jupyterhub/tests directory in the git repository.

## Running the tests¶

1. Make sure you have completed Setting up a development install. You should be able to start jupyterhub from the commandline & access it from your web browser. This ensures that the dev environment is properly set up for tests to run.

2. You can run all tests in JupyterHub

pytest --async-test-timeout 15 -v jupyterhub/tests


This should display progress as it runs all the tests, printing information about any test failures as they occur.

The --async-test-timeout parameter is used by pytest-tornado to set the asynchronous test timeout to 15 seconds rather than the default 5, since some of our tests take longer than 5s to execute.

3. You can also run tests in just a specific file:

pytest --async-test-timeout 15 -v jupyterhub/tests/<test-file-name>

4. To run a specific test only, you can do:

pytest --async-test-timeout 15 -v jupyterhub/tests/<test-file-name>::<test-name>


This runs the test with function name <test-name> defined in <test-file-name>. This is very useful when you are iteratively developing a single test.

For example, to run the test test_shutdown in the file test_api.py, you would run:

pytest -v jupyterhub/tests/test_api.py::test_shutdown


## Troubleshooting Test Failures¶

### All the tests are failing¶

Make sure you have completed all the steps in Setting up a development install sucessfully, and can launch jupyterhub from the terminal.

### Tests are timing out¶

The --async-test-timeout parameter to pytest is used by pytest-tornado to set the asynchronous test timeout to a higher value than the default of 5s, since some of our tests take longer than 5s to execute. If the tests are still timing out, try increasing that value even more. You can also set an environment variable ASYNC_TEST_TIMEOUT instead of passing --async-test-timeout to each invocation of pytest.