The correct choice is Multi stage Dockerfile.

Multi stage Dockerfile lets you run compilation and tests in one or more intermediate stages and then produce a final image that does not include the test outputs. This makes it straightforward to keep test artifacts only inside the build stages and not copy them into the final image or expose them as pipeline artifacts.

Docker Compose file defines and orchestrates multiple containers and it is useful for local integration scenarios, but it does not by itself provide the build stage isolation needed to guarantee that test outputs remain inside the pipeline build and are not propagated as artifacts.

Single stage Dockerfile builds everything into one image so tests and their outputs are part of the same build unless you perform explicit cleanup, and that makes it harder to ensure outputs are not included in the final image or published by the pipeline.

Google Kubernetes Engine pod runs workloads on an external cluster and is not relevant to keeping test outputs strictly inside an Azure DevOps build stage. Running tests on GKE would move execution outside the build environment and could lead to persistence or collection of outputs that violates the requirement.

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