Added documentation

monkey/monkey_island/cc/models/monkey_ttl.py

@@ -2,6 +2,15 @@ from mongoengine import Document, DateTimeField
 
 
 class MonkeyTtl(Document):
+    """
+    This model represents the monkey's TTL, and is referenced by the main Monkey document.
+    See https://docs.mongodb.com/manual/tutorial/expire-data/ and
+    https://stackoverflow.com/questions/55994379/mongodb-ttl-index-doesnt-delete-expired-documents/56021663#56021663
+    for more information about how TTL indexing works.
+
+    When initializing this object, do it like so:
+    t = MonkeyTtl(expire_at=datetime.utcnow() + timedelta(seconds=XXX))
+    """
     meta = {
         'indexes': [
             {

monkey/monkey_island/cc/models/test_monkey.py

@@ -13,6 +13,7 @@ from monkey_ttl import MonkeyTtl
 
 class TestMonkey(TestCase):
     def test_is_dead(self):
+        # Arrange
         alive_monkey_ttl = MonkeyTtl(expire_at=datetime.now() + timedelta(seconds=30))
         alive_monkey_ttl.save()
         alive_monkey = Monkey(
@@ -21,24 +22,30 @@ class TestMonkey(TestCase):
             ttl_ref=alive_monkey_ttl.id)
         alive_monkey.save()
 
+        # MIA stands for Missing In Action
         mia_monkey_ttl = MonkeyTtl(expire_at=datetime.now() + timedelta(seconds=30))
         mia_monkey_ttl.save()
         mia_monkey = Monkey(guid=str(uuid.uuid4()), dead=False, ttl_ref=mia_monkey_ttl)
         mia_monkey.save()
-        # Emulate timeout
+        # Emulate timeout - ttl is manually deleted here, since we're using mongomock and not a real mongo instance.
         sleep(1)
         mia_monkey_ttl.delete()
 
         dead_monkey = Monkey(guid=str(uuid.uuid4()), dead=True)
         dead_monkey.save()
 
+        # act + assert
         self.assertTrue(dead_monkey.is_dead())
         self.assertTrue(mia_monkey.is_dead())
         self.assertFalse(alive_monkey.is_dead())
 
     def test_get_single_monkey_by_id(self):
+        # Arrange
         a_monkey = Monkey(guid=str(uuid.uuid4()))
         a_monkey.save()
 
+        # Act + assert
+        # Find the existing one
         self.assertIsNotNone(Monkey.get_single_monkey_by_id(a_monkey.id))
+        # Raise on non-existent monkey
         self.assertRaises(MonkeyNotFoundError, Monkey.get_single_monkey_by_id, "abcdefabcdefabcdefabcdef")