docker-compose-tests

Reach for Compose in tests when the SUT has two or more real backing services that must see each other (app -> db -> cache -> queue), the same topology must run locally and in CI without imperative drift, or parallel CI jobs each need an isolated stack. For a single dependency wired into one test, testcontainers is lighter - it lives inside the test process with no separate docker compose up step.

Step 1 - Author compose.test.yaml

Compose's default file lookup is compose.yaml or docker-compose.yaml in the working directory or any parent (compose-cli); using the explicit compose.test.yaml filename + -f flag keeps test topology separate from local-dev topology.