Endpoints_OpenApi test fails under Docker-outside-of-Docker (bind-mount source resolved on host)

[C0nquistadore]

Summary

CodeGenerationTaskTests.Endpoints_OpenApi fails when the test suite runs inside a container that talks to the Docker daemon via Docker-outside-of-Docker (DooD) — e.g. the .devcontainer added in the agent-workspace setup, or any CI runner that mounts the host Docker socket.

Repro

dotnet test tests/Dibix.Sdk.Tests/Dibix.Sdk.Tests.csproj --filter "FullyQualifiedName~Endpoints_OpenApi"

from inside the devcontainer.

Observed

Docker.DotNet.DockerApiException: Docker API responded with status code='BadRequest',
response='{"message":"invalid mount config for type \"bind\": bind source path does not exist:
/workspace/tests/Dibix.Sdk.Tests/bin/Debug/net10.0/Output/Endpoints_OpenApi"}'

Stack originates at TestContainerExtensions.StartAsync →
CodeGenerationTaskTests.AssertOpenApiFileCodeGeneration (tests/Dibix.Sdk.Tests/CodeGeneration/CodeGenerationTaskTests.Base.cs:344).

Root cause

AssertOpenApiFileCodeGeneration validates the generated OpenAPI document by starting a sibling node:25-alpine container and bind-mounting the test output directory into it (CodeGenerationTaskTests.Base.cs:331):

new ContainerBuilder("node:25-alpine")
    .WithBindMount(directory, "/app")   // directory = TestRunResultsDirectory/Output/<TestName>
    ...

Under DooD the Docker daemon is the host daemon, so a bind-mount source path is resolved on the host filesystem, not inside the devcontainer. The path /workspace/tests/.../Output/Endpoints_OpenApi only exists inside the devcontainer (it lives under the bind-mounted workspace at a container-only sub-path), so the daemon rejects the mount.

This is a structural DooD limitation, not a flaky test: bind-mounting a container-local path into a sibling container cannot work unless the path is also present at the same absolute location on the host.

Notes / workarounds

• There is already an escape hatch: Configuration.HasNoTestContainerSupport (CodeGenerationTaskTests.Base.cs:322) short-circuits the validation. Setting it via the test appsettings.json / run settings makes the suite pass (105 passed, this one skipped) but skips OpenAPI validation entirely.
• Every other Testcontainers-backed suite passes in the same devcontainer (Dibix.Dapper.Tests, Dibix.Http.Host.Tests), because they don't bind-mount container-local paths — they only start SQL Server and connect over TCP.

Possible fixes

• Replace the bind-mount with copying the file(s) into the container (WithResourceMapping / tar copy) and reading results back via the API, so no host-path assumption is made.
• Or detect DooD (e.g. TESTCONTAINERS_HOST_OVERRIDE set / socket is host) and auto-skip with a clear message instead of a hard failure.

Environment

• .devcontainer (Ubuntu 24.04, .NET 10 SDK) with docker-outside-of-docker feature, host Docker socket mounted, TESTCONTAINERS_HOST_OVERRIDE=host.docker.internal.