parallelization for unit tests (#5000)

* parallelization for unit tests

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>

.circleci/config.yml

@@ -175,6 +175,7 @@ jobs:
             done
 
   unitTests:
+    parallelism: 6
     executor: besu_executor_xl
     steps:
       - prepare
@@ -184,7 +185,14 @@ jobs:
           name: Build
           no_output_timeout: 20m
           command: |
-            ./gradlew --no-daemon build
+            GRADLE_ARGS=$(ls -d */src/test/java \
+              | sed 's/^/:/' \
+              | sed 's@src/test/java@@' \
+              | sed 's@/@:test@' \
+              | circleci tests split --split-by=timings)
+            # Format the arguments to "./gradlew test"
+            echo "Prepared arguments for Gradle: $GRADLE_ARGS"
+            ./gradlew --no-daemon $GRADLE_ARGS
       - capture_test_results
 
   integrationTests: