I've been coding in Python professionally for almost ten years, mostly working with Django, but have also written many Python-only libraries and applications. On all the projects I work and have worked on, testing is a strong focus, between owning the CI, speeding up tests and developing testing tools to make life easier.
Especially lately I've been focusing on reshaping the tests we write at Xelix to make them more maintainable and easier to write, and faster to run. This has lead to me writing private documentation, and writing a couple of pytest plugins, both private and public. The public ones include: detecting unused fixtures (https://github.com/mikicz/pytest-unused-fixtures), and analysing worker usage when running xdist (https://github.com/mikicz/pytest-xdist-worker-stats).
At both of my current and past places of work, I've endeavoured to use Django and Django libraries to best suite the business needs, which meant a lot of experimenting, especially with functionality that Postgres provides, like schemas and materialized views. I maintain an internal fork of django-tenants that allows us to use it without subdomains, and maintain a library for managing Postgres views and materialized views from Django. (https://github.com/xelixdev/django-pgviews-redux)