Nightly integration tests for gRPC communication between Mu-Scala and Mu-Haskell.

How it works

1. Clones the Mu-Scala repo (which is where the tests live)
2. Updates stack.yaml to use the master branch of Mu-Haskell instead of the latest release version
3. Builds the cb372/mu-scala-haskell-integration-tests Docker image
4. Runs the tests: sbt haskell-integration-tests/test

This means it is testing the master HEAD of Mu-Scala against the master HEAD of Mu-Haskell every night.

Where it runs

The tests run every night on CircleCI.

They can't run as a GitHub Actions workflow because building the Docker image needs too much disk space.

They used to run on Travis CI until it stopped being free.