"Testing, testing, testing, to get started with automated ETL (ELT) testing have a look here: https://the.agilesql.club/etl-testing/
TLDR: There is a new exciting community slack channel where you can find a mentor, a mentee or both if that floats your boat. The great Chrissy LeMaire (https://twitter.com/cl) from dba tools and sqlcommunity.slack.com fame and general Powershell and SQL legend has started a new mentor's slack channel.
Come and join the fun, it is a community-driven informal process. I have put up a google docs sheet with a list that people can add themselves to or use to contact other people who might be a good fit for them.
There are no rules this is run by the community, do whatever you feel is good but if you start in a mentee/mentor relationship then I would encourage you to read up on how to make it a success and one of the first things is to work out what success looks like for both parties and when the mentee/mentor relationship should end and what that looks like, have a read:
The initial set of mentors are mostly, but this is open to anyone, you have management experience? Great, you have startup experience, great? You have enterprise experience? Great, you have any knowledge of anything? Great. Everyone's experience is unique and if you feel you would benefit by being a mentor or a mentee or both then get involved, what have you got to lose?
Mentoring isn't a one-way thing, in a good mentoring relationship you will both gain :)
To join THE slack go to https://dbatools.io/slack/ then go to #mentors