Configure Docker on CI

[wilkinsona]

With the recent addition of Testcontainers to the test suite, we need to configure CI to make Docker available.

[wilkinsona]

Hijacking the CI container and running the build results in FormatterIntegrationTests – the tests that use Testcontainers – being skipped:

[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
16:19:13.797 [main] ERROR org.testcontainers.dockerclient.DockerClientProviderStrategy - Could not find a valid Docker environment. Please check configuration. Attempted configurations were:
16:19:13.801 [main] ERROR org.testcontainers.dockerclient.DockerClientProviderStrategy -     UnixSocketClientProviderStrategy: failed with exception InvalidConfigurationException (Could not find unix domain socket). Root cause NoSuchFileException (/var/run/docker.sock)
16:19:13.801 [main] ERROR org.testcontainers.dockerclient.DockerClientProviderStrategy -     UnixSocketClientProviderStrategy: failed with exception InvalidConfigurationException (Could not find unix domain socket). Root cause NoSuchFileException (/var/run/docker.sock)
16:19:13.801 [main] ERROR org.testcontainers.dockerclient.DockerClientProviderStrategy - As no valid configuration was found, execution cannot continue
[INFO] Running io.spring.javaformat.formatter.FormatterIntegrationTests
[WARNING] Tests run: 1, Failures: 0, Errors: 0, Skipped: 1, Time elapsed: 0.001 s - in io.spring.javaformat.formatter.FormatterIntegrationTests

When run as part of the CI build, the tests fail but the related output is pretty minimal:

05:54:18
[ERROR] Errors: 
[ERROR]   FormatterIntegrationTests.formatCode:56 ? ContainerLaunch Container startup fa...
[ERROR]   FormatterIntegrationTests.formatCode:56 ? ContainerLaunch Container startup fa...
[ERROR]   FormatterIntegrationTests.formatCode:56 ? ContainerLaunch Container startup fa...

[wilkinsona]

With the Docker daemon started in the hijacked container, the tests then fail due to Docker Hub's rate limiting.