Few months ago in the office we started a discussion about testing.
The original topic was “how to implement a continuous integration/continuous delivery workflow”, so “how to test” became immediately a requirement and a parallel important topic.
My suggestion was to start coding in TDD of course, but like every office we had a lot of legacy code to deal with.
In order not to be stuck by that, we decided temporarily to focus on new (or almost new) projects and apply it to them.
So the point became to find a way to have all the developers, regardless on the seniority and the project, on the same page about the topic.