Run CI Against Podman

[Thomascountz]

The existing podman-rspec job in the unit_test.yaml workflow only installed Podman, but never started the engine. As a result the tets still talked to the pre-installed Docker daemon on /var/run/docker.sock, since that's what it defaults to. Docker.podman? never returned true and we were silently re-running the test suite with Docker.

https://github.com/actions/runner-images/blob/27d8a9d9026ab6e207340dde6e14f4faf3864e29/images/ubuntu/scripts/build/install-docker.sh#L60-L61

You can see that in the podman-rspec test runs, there are no specs skipped due to skip('Not supported on podman') if ::Docker.podman?, meaning we're not using Podman.

Proposed solution

1. Start a real Podman API service

podman system service unix://… is launched in the runner’s home directory and kept alive for the whole job.

2. Point the test suite at that socket

We export DOCKER_HOST so the gem connects to Podman, and set an EXPECT_PODMAN flag.

3. Fail fast if mis-configured

A guard in spec_helper.rb hard-exits when EXPECT_PODMAN=true but Docker.podman? is still false.

4. Remove Podman installation (Maybe?)

Podman is already pre-installed on GitHub Ubuntu runners so the custom install script is no longer called. But, perhaps it's better to keep it to ensure it's always available.

Additional notes

• The new guard is a no-op in local development unless you explicitly set EXPECT_PODMAN=true.
• If the Podman socket fails to start or the environment is mis-wired, the build fails immediately with a clear error message.
• No additional packages or elevated privileges are required; the service runs rootless in the runner’s home directory.
• Docker workflow remains unchanged and continues to validate against multiple Docker Engine versions.

[Thomascountz]

Running against Podman locally and on my fork, I get these failures consistently.

Failures:

  1) Docker::Connection#resource resource 
     Failure/Error: its(:resource) { should be_a Excon::Connection }
     
     NoMethodError:
       private method `resource' called for an instance of Docker::Connection
     # ./spec/docker/connection_spec.rb:69:in `block (3 levels) in <top (required)>'

  2) Docker::Image.create with a block capturing create output calls the block and passes build output
     Failure/Error: expect(create_output).to match(/ulling.*busybox/)
     
       expected "{\"status\":\"Pulling fs layer\",\"progressDetail\":{},\"id\":\"086517b4ab5d\"}\n{\"status\":\"Downl...7f65c9eee073\"}\n{\"status\":\"Download complete\",\"progressDetail\":{},\"id\":\"7f65c9eee073\"}\n" to match /ulling.*busybox/
       Diff:
       @@ -1 +1,5 @@
       -/ulling.*busybox/
       +{"status":"Pulling fs layer","progressDetail":{},"id":"086517b4ab5d"}
       +{"status":"Download complete","progressDetail":{},"id":"086517b4ab5d"}
       +{"status":"Pulling fs layer","progressDetail":{},"id":"7f65c9eee073"}
       +{"status":"Download complete","progressDetail":{},"id":"7f65c9eee073"}
       +{"status":"Download complete","progressDetail":{},"id":"7f65c9eee073"}
       
     # ./spec/docker/image_spec.rb:479:in `block (4 levels) in <top (required)>'

  3) Docker::Image#push when there are no credentials still pushes
     Failure/Error: expect { raise(ex) }.to_not raise_error
     
       expected no Exception, got #<Docker::Error::ServerError:"{\"errorDetail\":{\"message\":\"trying to reuse blob sha256:83df073ecb7...5000: Get \\\"https://localhost:5000/v2/\\\": http: server gave HTTP response to HTTPS client\"}\n"> with backtrace:
         # ./lib/docker/connection.rb:91:in `rescue in request'
         # ./lib/docker/connection.rb:46:in `request'
         # ./lib/docker/connection.rb:111:in `block (2 levels) in <class:Connection>'
         # ./lib/docker/image.rb:37:in `push'
         # ./spec/docker/image_spec.rb:220:in `block (4 levels) in <top (required)>'
     # ./spec/docker/image_spec.rb:225:in `rescue in block (4 levels) in <top (required)>'
     # ./spec/docker/image_spec.rb:219:in `block (4 levels) in <top (required)>'
     # ------------------
     # --- Caused by: ---
     # Excon::Error::InternalServerError:
     #   Expected([200, 201, 202, 203, 204, 301, 304]) <=> Actual(500 InternalServerError)
     #   ./vendor/bundle/ruby/3.3.0/gems/excon-1.2.7/lib/excon/middlewares/expects.rb:13:in `response_call'

Finished in 1 minute 43.63 seconds (files took 1.07 seconds to load)
221 examples, 3 failures, 31 pending

Failed examples:

rspec ./spec/docker/connection_spec.rb:69 # Docker::Connection#resource resource 
rspec ./spec/docker/image_spec.rb:477 # Docker::Image.create with a block capturing create output calls the block and passes build output
rspec ./spec/docker/image_spec.rb:218 # Docker::Image#push when there are no credentials still pushes