run grails tests in parallel

test_all_parallel.sh

#! /usr/bin/env bash
command -v parallel >/dev/null 2>&1 || { echo >&2 "Please install parallel via brew: brew install parallel"; exit 1; }

BASE_DIR=$(cd "$(dirname "$0")"; pwd -P)/..
PARALLEL_WORKERS=2

export GRAILS_OPTS="-Xmx2G -Xms2g -XX:MaxPermSize=500m"

OPEN_TESTLOG_AND_FAIL="( open target/test-reports/html/index.html && exit 1 )"
TEST_APP="( grails test-app --non-interactive || $OPEN_TESTLOG_AND_FAIL )"

# run all commands in the heredoc in parallel, echo out full lines as they're collected with no more than $PARALLEL_WORKERS at at time
SHELL=/bin/bash parallel --ungroup --line-buffer -j $PARALLEL_WORKERS --no-notice << $EOF
    $BASE_DIR/bin/testAllKarma.sh  # script in same directory to run karma tests
    echo "running test-app" && $TEST_APP
$EOF

PARALLEL_EXIT_CODE=$?
if [[ $PARALLEL_EXIT_CODE != 0 ]]; then
    echo "Error running tests"
    exit $PARALLEL_EXIT_CODE
else
    echo "All tests passed successfully"
fi  

If you want to run unit/integration/functional also in parallel, you can by making new lines for those in the parallel EOF heredoc, but you'll want to make sure that you're setting up unique working directories for each of them so they don't collide.