Neil Gall - System testing with Pytest, Docker, and Flask

System testing with Pytest, Docker, and Flask
[EuroPython 2018 - Talk - 2018-07-27 - Moorfoot]
[Edinburgh, UK]

By Neil Gall

The composability of fixtures in pytest is an improvement over traditional
xUnit setup/teardown, reducing the incentive to commit testing crimes such as
multi-stage and stepwise tests. This is great out of the box for unit tests,
but I'm going to show how to combine the power of pytest fixtures with Docker
to build high-level integration tests for microservices or other complex
systems with multiple components. I'll then build on that to show how to embed
mock web services written with Flask right into the test code.

With a sample Java application that makes use of some external resources to
offer a data processing service I'll first quick an overview of Pytest, Docker,
and Flask. Then I'll mix some pre-built code with live test coding to
demonstrate how to build high-level system tests which spin up the application
and its dependencies in Docker. I'll then mock one of the external dependencies
using Flask, allowing the test to control and verify interaction between the
system components. Finally I'll show how to wrap the Flask application in a
WSGI middleware that lets the test inspect interaction with the mocked service.

From a learning and development point of view, building your own is better than
re-using someone else's code so I'll show how the support code for these
features is relatively simple and how the audience can build it themselves to
exactly meet their own needs. And I'll do it all with a sense of fun, a joke
or two and maybe a little storytelling.

[patrikwihlke]

Great talk, Neil! Found it very useful

[CaptainNEO]

Hey thank you @Niel. That idea was great but why we just run test inside docker compose?