I had numerous issues related to particular backends. If you go deeper, i even had Postgres-related issue which only occurred on python3.6 (python 3.5 worked fine. It was related to parsing DB URL :) ). For sure testing all matrix combination is an overkill, but we need to test all backends. I also had a number of issues between python 3.5 and 3.6 (blogpost in the making !) so we need to test both 3.5 and 3.6. When we looked at Pypi stats we have like 70% of python 3.6 users but 3.5 is important to support because stable Debian (till mid July) ships with python 3.5.
The proposal we have now with new Docker image we have this set of tests which i think is "good enough": - Python: 3.6 BACKEND=mysql ENV=docker - Python: 3.6 BACKEND=postgres ENV=docker - Python: 3.5 BACKEND=sqlite ENV=docker - Python: 3.6 BACKEND=postgres ENV=kubernetes KUBERNETES_VERSION=v1.13.0 You can see it here: https://travis-ci.org/apache/airflow/builds/551584527 I hope I will get Fokko/Ash's blessing soon to merge it ;) - I think we are waiting for 1.10.4 to be released. J.
