Bonus: Testing the Application

Now that you have finished the application and everything works as expected, it’s probably not a bad idea to add automated tests to simplify modifications in the future. The application above is used as a basic example of how to perform unit testing in the Testing Flask Applications section of the documentation. Go there to see how easy it is to test Flask applications.

Adding tests to flaskr

Assuming you have seen the Testing Flask Applications section and have either written your own tests for flaskr or have followed along with the examples provided, you might be wondering about ways to organize the project.

One possible and recommended project structure is:


For now go ahead a create the tests/ directory as well as the file.

Running the tests

At this point you can run the tests. Here pytest will be used.


Make sure that pytest is installed in the same virtualenv as flaskr. Otherwise pytest test will not be able to import the required components to test the application:

pip install -e .
pip install pytest

Run and watch the tests pass, within the top-level flaskr/ directory as:


Testing + setuptools

One way to handle testing is to integrate it with setuptools. Here that requires adding a couple of lines to the file and creating a new file setup.cfg. One benefit of running the tests this way is that you do not have to install pytest. Go ahead and update the file to contain:

from setuptools import setup


Now create setup.cfg in the project root (alongside


Now you can run:

python test

This calls on the alias created in setup.cfg which in turn runs pytest via pytest-runner, as the script has been called. (Recall the setup_requires argument in Following the standard rules of test-discovery your tests will be found, run, and hopefully pass.

This is one possible way to run and manage testing. Here pytest is used, but there are other options such as nose. Integrating testing with setuptools is convenient because it is not necessary to actually download pytest or any other testing framework one might use.