diff --git a/Makefile b/Makefile
index 42a11f1..b15329f 100644
--- a/Makefile
+++ b/Makefile
@@ -26,7 +26,7 @@ MODULE=cwltest
 # `SHELL=bash` doesn't work for some, so don't use BASH-isms like
 # `[[` conditional expressions.
 PYSOURCES=$(wildcard ${MODULE}/**.py tests/*.py) setup.py
-DEVPKGS=pep8 diff_cover autopep8 pylint coverage pep257 flake8 pytest
+DEVPKGS=pep8 diff_cover autopep8 pylint coverage pep257 flake8 pytest pytest-xdist
 DEBDEVPKGS=pep8 python-autopep8 pylint python-coverage pep257 sloccount python-flake8
 VERSION=1.0.$(shell date +%Y%m%d%H%M%S --utc --date=`git log --first-parent \
 	--max-count=1 --format=format:%cI`)
@@ -132,7 +132,7 @@ diff-cover.html: coverage-gcovr.xml coverage.xml
 
 ## test        : run the ${MODULE} test suite
 test: all
-	./setup.py test
+	./setup.py test --addopts -n$(shell nproc)
 
 sloccount.sc: ${PYSOURCES} Makefile
 	sloccount --duplicates --wide --details $^ > sloccount.sc
diff --git a/release-test.sh b/release-test.sh
index e4a77ec..e098f89 100755
--- a/release-test.sh
+++ b/release-test.sh
@@ -6,7 +6,7 @@ set -x
 package=cwltest
 module=cwltest
 repo=https://github.com/common-workflow-language/cwltest.git
-run_tests="py.test --pyarg ${module}"
+run_tests="py.test --pyarg ${module} -n$(nproc)"
 pipver=8.0.1 # minimum required version of pip
 setupver=20.10.1 # minimum required version of setuptools
 PYVER=${PYVER:=2.7}