I didn't mention, but the testcontainer code also preferred to add that network io to the actual test runtime, which made measuring the test's performance harder, and meant we couldn't as safely cache the test's results. The bazel version made it easy to build the test's dependency as part of the test compilation process (as it should be) so the test runtime didn't have to do external network IO.

"Excels" is also a stretch; we had a few hundred tests launching dedicated redis servers, and with hand-rolled code, that worked fine with zero flakes. With testcontainers, it regularly flaked with some opaque docker network error or sometimes just plain a timeout because apparently launching 100s of containers in parallel is a hard problem for docker or something.

I'm sure it works well for some people, but if those people wanted to build out their own version without docker and testcontainers, specific to their development tooling and environment, it would probably work better in most cases I think.