diff --git a/jenkins.bash b/jenkins.bash
index bec40c2de..583fe6607 100755
--- a/jenkins.bash
+++ b/jenkins.bash
@@ -14,29 +14,40 @@ cloneorpull() {
 }
 venv() {
         if ! test -d "$1" ; then
-                virtualenv "$1"
+                virtualenv -p python${PYTHON_VERSION} "$1"
         fi
 	# shellcheck source=/dev/null
         source "$1"/bin/activate
 }
-git clean --force -d -x || /bin/true
+
 cloneorpull common-workflow-language https://github.com/common-workflow-language/common-workflow-language.git
-venv cwltool-venv
 docker pull node:slim
-export PIP_DOWNLOAD_CACHE=/var/lib/jenkins/pypi-cache/
-pip install -U setuptools wheel pip
-python setup.py install
-pip install "cwltest>=1.0.20160825151655"
-pushd common-workflow-language
+# clean both the repos before the loop
 git clean --force -d -x || /bin/true
-# shellcheck disable=SC2154
-if [[ "$version" = *dev* ]]
-then
-	EXTRA="EXTRA=--enable-dev"
-fi
-./run_test.sh --junit-xml=result.xml RUNNER=cwltool -j4 DRAFT="${version}" ${EXTRA}
-CODE=$?
-popd
+git -C common-workflow-language clean --force -d -x || /bin/true
+
+# Test for Python 2.7 and Python 3
+for PYTHON_VERSION in 2.7 3
+do
+	venv cwltool-venv${PYTHON_VERSION}
+	export PIP_DOWNLOAD_CACHE=/var/lib/jenkins/pypi-cache/
+	# use pip2.7 and pip3 in separate loop runs
+	pip${PYTHON_VERSION} install -U setuptools wheel pip
+	pip${PYTHON_VERSION} install .
+	pip${PYTHON_VERSION} install "cwltest>=1.0.20160825151655"
+	pushd common-workflow-language
+	# shellcheck disable=SC2154
+	if [[ "$version" = *dev* ]]
+	then
+		EXTRA="EXTRA=--enable-dev"
+	fi
+	./run_test.sh --junit-xml=result${PYTHON_VERSION}.xml RUNNER=cwltool -j4 DRAFT=${version}
+	CODE=$(($CODE+$?)) # capture return code of ./run_test.sh
+	deactivate
+	popd
+done
+
+# build new docker container
 if [ "$GIT_BRANCH" = "origin/master" ] && [[ "$version" = "v1.0" ]]
 then
   ./build-cwl-docker.sh && docker push commonworkflowlanguage/cwltool_module && docker push commonworkflowlanguage/cwltool