Instructions on ray-java test

1. Install necessary executables

• java and javac is needed to run ray-java tests, and users need to make sure they're accessible in $PATH
• You could check whether they're installed by which java and which javac
• Install java with sudo apt install openjdk-11-jre -y
• Install javac with sudo apt install openjdk-11-jdk -y
• java-11 is the version we use on CI

2. Run java test with bazel

# To run ray tests.
bazel test //java:all_tests --test_output=streamed
# To run custom tests.
bazel test //java:custom_test --test_output=streamed