Apache Drill patches some Protobuf and Guava classes (see GuavaPatcher, ProtobufPatcher), patching should be done before classes to be patched are loaded. That's why this operation is executed in static block in Drillbit class.
Some tests in java-exec module use Drillbit class, some extend DrillTest class, both of them patch Guava. But there are some tests that do not call patcher but load classes to be patched. For example, org.apache.drill.exec.sql.TestSqlBracketlessSyntax loads Guava Preconditions class. If such tests run before tests that require patching, tests run will fail since patching won't be successful. Patchers code does not fail application if patching was not complete, just logs warning (logger.warn("Unable to patch Guava classes.", e);), so sometimes it hard to identify unit tests failure root cause.
We need to revisit all Drill tests to ensure that all of them extend common test base class which patchers Protobuf and Guava classes in static block. Also refactor Patcher classes to have assert to fail if patching fails during unit testing if there are any problems.
After all tests are revised, we can remove metastore-test execution from main.xml in maven-surefire-plugin which was added to ensure that all Metastore tests run in a separate JVM where patching is done in first place since Iceberg Metastore heavily depends on patched Guava Preconditions class.