That's understandable and the reason we have three environments. One for Unit tests, one for automation and one for CI. There's advantages and disadvantages to having one large environment compared to multiple, but it's worked for us so far and TC adding 100 build configurations has helped.
It works great with containers, but we don't do anything advanced with Docker. A lot more time was spent spinning up 2016 agent servers, enabling and configuring Docker on Windows and all the dev work for it to work with swarm.
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