add some unit tests for the os_server module

This commit adds some unit tests for the `cloud.openstack.os_server`
module.  These tests exercise `_network_args` thoroughly and
`_create_server` lightly.

These tests will **fail** until ansible/ansible-modules-core#2275 lands.

To run the tests:

    pip install -r test-requirements.txt
    PYTHONPATH=$PWD py.test

Originally from ansible/ansible-modules-core@3387526bca

test/unit/cloud/openstack/test_os_server.py

@@ -0,0 +1,221 @@
+import mock
+import pytest
+import yaml
+import inspect
+import collections
+
+from cloud.openstack import os_server
+
+
+class AnsibleFail(Exception):
+    pass
+
+
+class AnsibleExit(Exception):
+    pass
+
+
+def params_from_doc(func):
+    '''This function extracts the docstring from the specified function,
+    parses it as a YAML document, and returns parameters for the os_server
+    module.'''
+
+    doc = inspect.getdoc(func)
+    cfg = yaml.load(doc)
+
+    for task in cfg:
+        for module, params in task.items():
+            for k, v in params.items():
+                if k in ['nics'] and type(v) == str:
+                    params[k] = [v]
+        task[module] = collections.defaultdict(str,
+                                               params)
+
+    return cfg[0]['os_server']
+
+
+class FakeCloud (object):
+    ports = [
+        {'name': 'port1', 'id': '1234'},
+        {'name': 'port2', 'id': '4321'},
+    ]
+
+    networks = [
+        {'name': 'network1', 'id': '5678'},
+        {'name': 'network2', 'id': '8765'},
+    ]
+
+    images = [
+        {'name': 'cirros', 'id': '1'},
+        {'name': 'fedora', 'id': '2'},
+    ]
+
+    flavors = [
+        {'name': 'm1.small', 'id': '1', 'flavor_ram': 1024},
+        {'name': 'm1.tiny', 'id': '2', 'flavor_ram': 512},
+    ]
+
+    def _find(self, source, name):
+        for item in source:
+            if item['name'] == name or item['id'] == name:
+                return item
+
+    def get_image_id(self, name, exclude=None):
+        image = self._find(self.images, name)
+        if image:
+            return image['id']
+
+    def get_flavor(self, name):
+        return self._find(self.flavors, name)
+
+    def get_flavor_by_ram(self, ram, include=None):
+        for flavor in self.flavors:
+            if flavor['ram'] >= ram and (include is None or include in
+                                         flavor['name']):
+                return flavor
+
+    def get_port(self, name):
+        return self._find(self.ports, name)
+
+    def get_network(self, name):
+        return self._find(self.networks, name)
+
+    create_server = mock.MagicMock()
+
+
+class TestNetworkArgs(object):
+    '''This class exercises the _network_args function of the
+    os_server module.  For each test, we parse the YAML document
+    contained in the docstring to retrieve the module parameters for the
+    test.'''
+
+    def setup_method(self, method):
+        self.cloud = FakeCloud()
+        self.module = mock.MagicMock()
+        self.module.params = params_from_doc(method)
+
+    def test_nics_string_net_id(self):
+        '''
+        - os_server:
+            nics: net-id=1234
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['net-id'] == '1234')
+
+    def test_nics_string_net_id_list(self):
+        '''
+        - os_server:
+            nics: net-id=1234,net-id=4321
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['net-id'] == '1234')
+        assert(args[1]['net-id'] == '4321')
+
+    def test_nics_string_port_id(self):
+        '''
+        - os_server:
+            nics: port-id=1234
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['port-id'] == '1234')
+
+    def test_nics_string_net_name(self):
+        '''
+        - os_server:
+            nics: net-name=network1
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['net-id'] == '5678')
+
+    def test_nics_string_port_name(self):
+        '''
+        - os_server:
+            nics: port-name=port1
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['port-id'] == '1234')
+
+    def test_nics_structured_net_id(self):
+        '''
+        - os_server:
+            nics:
+                - net-id: '1234'
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['net-id'] == '1234')
+
+    def test_nics_structured_mixed(self):
+        '''
+        - os_server:
+            nics:
+                - net-id: '1234'
+                - port-name: port1
+                - 'net-name=network1,port-id=4321'
+        '''
+        args = os_server._network_args(self.module, self.cloud)
+        assert(args[0]['net-id'] == '1234')
+        assert(args[1]['port-id'] == '1234')
+        assert(args[2]['net-id'] == '5678')
+        assert(args[3]['port-id'] == '4321')
+
+
+class TestCreateServer(object):
+    def setup_method(self, method):
+        self.cloud = FakeCloud()
+        self.module = mock.MagicMock()
+        self.module.params = params_from_doc(method)
+        self.module.fail_json.side_effect = AnsibleFail()
+        self.module.exit_json.side_effect = AnsibleExit()
+
+        self.meta = mock.MagicMock()
+        self.meta.gett_hostvars_from_server.return_value = {
+            'id': '1234'
+        }
+        os_server.meta = self.meta
+
+    def test_create_server(self):
+        '''
+        - os_server:
+            image: cirros
+            flavor: m1.tiny
+            nics:
+              - net-name: network1
+        '''
+        with pytest.raises(AnsibleExit):
+            os_server._create_server(self.module, self.cloud)
+
+        assert(self.cloud.create_server.call_count == 1)
+        assert(self.cloud.create_server.call_args[1]['image']
+               == self.cloud.get_image_id('cirros'))
+        assert(self.cloud.create_server.call_args[1]['flavor']
+               == self.cloud.get_flavor('m1.tiny')['id'])
+        assert(self.cloud.create_server.call_args[1]['nics'][0]['net-id']
+               == self.cloud.get_network('network1')['id'])
+
+    def test_create_server_bad_flavor(self):
+        '''
+        - os_server:
+            image: cirros
+            flavor: missing_flavor
+            nics:
+              - net-name: network1
+        '''
+        with pytest.raises(AnsibleFail):
+            os_server._create_server(self.module, self.cloud)
+
+        assert('missing_flavor' in
+               self.module.fail_json.call_args[1]['msg'])
+
+    def test_create_server_bad_nic(self):
+        '''
+        - os_server:
+            image: cirros
+            flavor: m1.tiny
+            nics:
+              - net-name: missing_network
+        '''
+        with pytest.raises(AnsibleFail):
+            os_server._create_server(self.module, self.cloud)
+
+        assert('missing_network' in
+               self.module.fail_json.call_args[1]['msg'])