From c8d7bcea7e1fd4b174e3be2a29e382df66e88b66 Mon Sep 17 00:00:00 2001
From: Tim Van Steenburgh <tvansteenburgh@gmail.com>
Date: Sat, 5 Nov 2016 21:47:29 -0400
Subject: [PATCH] Add ModelState tests

---
 juju/model.py            | 12 ++++-----
 tests/unit/test_model.py | 54 ++++++++++++++++++++++++++++++++++------
 tox.ini                  |  3 ++-
 3 files changed, 53 insertions(+), 16 deletions(-)

diff --git a/juju/model.py b/juju/model.py
index 953aa8f..db65b7d 100644
--- a/juju/model.py
+++ b/juju/model.py
@@ -159,14 +159,12 @@ class ModelState(object):
 
     def get_entity(
             self, entity_type, entity_id, history_index=-1, connected=True):
-        """Return an object instance representing the entity created or
-        updated by ``delta``
+        """Return an object instance for the given entity_type and id.
+
+        By default the object state matches the most recent state from
+        Juju. To get an instance of the object in an older state, pass
+        history_index, an index into the history deque for the entity.
 
-        """
-        """
-        log.debug(
-            'Getting %s:%s at index %s',
-            entity_type, entity_id, history_index)
         """
 
         if history_index < 0 and history_index != -1:
diff --git a/tests/unit/test_model.py b/tests/unit/test_model.py
index 97966da..f8cced3 100644
--- a/tests/unit/test_model.py
+++ b/tests/unit/test_model.py
@@ -1,22 +1,28 @@
 import unittest
 
+import mock
+
+
+def _make_delta(entity, type_, data=None):
+    from juju.client.client import Delta
+    from juju.delta import get_entity_delta
+
+    delta = Delta([entity, type_, data])
+    return get_entity_delta(delta)
+
 
 class TestObserver(unittest.TestCase):
     def _make_observer(self, *args):
         from juju.model import _Observer
         return _Observer(*args)
 
-    def _make_delta(self, entity, type_, data=None):
-        from juju.delta import ApplicationDelta
-        return ApplicationDelta([entity, type_, data])
-
     def test_cares_about_id(self):
         id_ = 'foo'
 
         o = self._make_observer(
             None, None, None, id_, None)
 
-        delta = self._make_delta(
+        delta = _make_delta(
             'application', 'change', dict(name=id_))
 
         self.assertTrue(o.cares_about(delta))
@@ -27,7 +33,7 @@ class TestObserver(unittest.TestCase):
         o = self._make_observer(
             None, type_, None, None, None)
 
-        delta = self._make_delta(
+        delta = _make_delta(
             type_, 'change', dict(name='foo'))
 
         self.assertTrue(o.cares_about(delta))
@@ -38,7 +44,7 @@ class TestObserver(unittest.TestCase):
         o = self._make_observer(
             None, None, action, None, None)
 
-        delta = self._make_delta(
+        delta = _make_delta(
             'application', action, dict(name='foo'))
 
         self.assertTrue(o.cares_about(delta))
@@ -50,7 +56,39 @@ class TestObserver(unittest.TestCase):
         o = self._make_observer(
             None, None, None, None, predicate)
 
-        delta = self._make_delta(
+        delta = _make_delta(
             'application', 'change', dict(fizz='bang'))
 
         self.assertTrue(o.cares_about(delta))
+
+
+class TestModelState(unittest.TestCase):
+    def test_apply_delta(self):
+        from juju.model import Model
+        from juju.application import Application
+
+        loop = mock.MagicMock()
+        model = Model(loop=loop)
+        delta = _make_delta('application', 'add', dict(name='foo'))
+
+        # test add
+        prev, new = model.state.apply_delta(delta)
+        self.assertEqual(
+            len(model.state.state[delta.entity][delta.get_id()]), 1)
+        self.assertIsNone(prev)
+        self.assertIsInstance(new, Application)
+
+        # test remove
+        delta.type = 'remove'
+        prev, new = model.state.apply_delta(delta)
+        # length of the entity history deque is now 3:
+        # - 1 for the first delta
+        # - 1 for the second delta
+        # - 1 for the None sentinel appended after the 'remove'
+        self.assertEqual(
+            len(model.state.state[delta.entity][delta.get_id()]), 3)
+        self.assertIsInstance(new, Application)
+        # new object is falsy because its data is None
+        self.assertFalse(new)
+        self.assertIsInstance(prev, Application)
+        self.assertTrue(prev)
diff --git a/tox.ini b/tox.ini
index f3cbbf8..5babec0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,6 +11,7 @@ skipsdist=True
 usedevelop=True
 passenv =
     HOME
-commands = py.test -rsx -s
+commands = py.test -rsx
 deps =
     pytest
+    mock
-- 
2.25.1