fixes nxos_evpn_vni and unittest (#24372)

* fixes nxos_evpn_vni

Signed-off-by: Trishna Guha <trishnaguha17@gmail.com>

* fixes pep8 issue and syntax error

* ansibot tole me to do this

* Unit test

test/units/modules/network/nxos/test_nxos_evpn_vni.py

@@ -0,0 +1,59 @@
+# (c) 2016 Red Hat Inc.
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+# Make coding more python3-ish
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+import json
+
+from ansible.compat.tests.mock import patch
+from ansible.modules.network.nxos import nxos_evpn_vni
+from .nxos_module import TestNxosModule, load_fixture, set_module_args
+
+
+class TestNxosEvpnVniModule(TestNxosModule):
+
+    module = nxos_evpn_vni
+
+    def setUp(self):
+        self.mock_run_commands = patch('ansible.modules.network.nxos.nxos_evpn_vni.run_commands')
+        self.run_commands = self.mock_run_commands.start()
+
+        self.mock_load_config = patch('ansible.modules.network.nxos.nxos_evpn_vni.load_config')
+        self.load_config = self.mock_load_config.start()
+
+        self.mock_get_config = patch('ansible.modules.network.nxos.nxos_evpn_vni.get_config')
+        self.get_config = self.mock_get_config.start()
+
+    def tearDown(self):
+        self.mock_run_commands.stop()
+        self.mock_load_config.stop()
+        self.mock_get_config.stop()
+
+    def load_fixtures(self, commands=None):
+        self.load_config.return_value = None
+
+    def test_nxos_evpn_vni_absent(self):
+        set_module_args(dict(vni='6000', state='absent'))
+        result = self.execute_module(changed=False)
+        self.assertEqual(result['commands'], [])
+
+    def test_nxos_evpn_vni_present(self):
+        set_module_args(dict(vni='6000', state='present'))
+        result = self.execute_module(changed=True)
+        self.assertEqual(result['commands'], ['evpn', 'vni 6000 l2'])