Bug 42787 create volume with label (#46527)

* add None value to docker-version so it can be mocked in tests

lib/ansible/module_utils/docker_common.py

@@ -110,6 +110,8 @@ BYTE_SUFFIXES = ['B', 'KB', 'MB', 'GB', 'TB', 'PB']
 
 
 if not HAS_DOCKER_PY:
+    docker_version = None
+
     # No docker-py. Create a place holder client to allow
     # instantiation of AnsibleModule and proper error handing
     class Client(object):

test/units/modules/cloud/docker/test_docker_volume.py

@@ -0,0 +1,31 @@
+# Copyright (c) 2018 Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+import json
+
+import pytest
+
+from ansible.modules.cloud.docker import docker_volume
+from ansible.module_utils import docker_common
+
+pytestmark = pytest.mark.usefixtures('patch_ansible_module')
+
+TESTCASE_DOCKER_VOLUME = [
+    {
+        'name': 'daemon_config',
+        'state': 'present'
+    }
+]
+
+
+@pytest.mark.parametrize('patch_ansible_module', TESTCASE_DOCKER_VOLUME, indirect=['patch_ansible_module'])
+def test_create_volume_on_invalid_docker_version(mocker, capfd):
+    mocker.patch.object(docker_common, 'HAS_DOCKER_PY', True)
+    mocker.patch.object(docker_common, 'docker_version', '1.8.0')
+
+    with pytest.raises(SystemExit):
+        docker_volume.main()
+
+    out, dummy = capfd.readouterr()
+    results = json.loads(out)
+    assert results['failed']
+    assert 'Error: docker / docker-py version is 1.8.0. Minimum version required is 1.10.0.' in results['msg']