diff --git a/.idea/misc.xml b/.idea/misc.xml
index f518f84..e659c40 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -54,7 +54,7 @@
     <ConfirmationsSetting value="0" id="Add" />
     <ConfirmationsSetting value="0" id="Remove" />
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_3" default="false" assert-keyword="false" jdk-15="false" project-jdk-name="Python 3.5.1 (C:\Users\Bradlee Speice\Anaconda3\python.exe)" project-jdk-type="Python SDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_3" default="false" assert-keyword="false" jdk-15="false" project-jdk-name="Python 2.7.12 virtualenv at ~/Development/metrik/py2-virt" project-jdk-type="Python SDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
   <component name="PythonCompatibilityInspectionAdvertiser">
diff --git a/metrik/merge.py b/metrik/merge.py
index d351d04..6266ccb 100644
--- a/metrik/merge.py
+++ b/metrik/merge.py
@@ -9,9 +9,9 @@ def open_connection(host, port):
     return MongoClient(host=host, port=port)
 
 
-def merge(con1, con2, database_name='metrik'):
-    database1 = con1[database_name]
-    database2 = con2[database_name]
+def merge(con1, con2, db1, db2):
+    database1 = con1[db1]
+    database2 = con2[db2]
     collections = database1.collection_names(include_system_collections=False)
     for collection_name in collections:
         collection1 = database1[collection_name]
@@ -37,14 +37,16 @@ def main():
                         help='The port number of the `left` database')
     parser.add_argument('-o', '--port-2', default=27017, dest='port2', type=int,
                         help='The port number of the `right` database')
-    parser.add_argument('-d', '--database', default='metrik',
-                        help='The database to merge from one host to the other')
+    parser.add_argument('-d', '--database-1', default='metrik', dest='db1',
+                        help='The database on the `left` host we are merging from')
+    parser.add_argument('-s', '--database-2', default='metrik', dest='db2',
+                        help='The database on the `right` host we are merging into')
     parser.add_argument('-v', '--version', action='version', version=__version__)
     args = parser.parse_args()
 
     con1 = open_connection(args.host1, args.port1)
     con2 = open_connection(args.host2, args.port2)
-    merge(con1, con2, args.database)
+    merge(con1, con2, args.db1, args.db2)
     con1.close()
     con2.close()
 
diff --git a/test/test_merge.py b/test/test_merge.py
new file mode 100644
index 0000000..83643a1
--- /dev/null
+++ b/test/test_merge.py
@@ -0,0 +1,35 @@
+import random, string
+
+from metrik.merge import merge, open_connection
+from metrik.conf import get_config
+from test.mongo_test import MongoTest
+
+
+class MergeTest(MongoTest):
+    db2_name = 'metrik_test_2'
+    collection_name = 'merge_test'
+
+    def setUp(self):
+        super(MergeTest, self).setUp()
+        self.client2 = self.client
+        self.db2 = self.client2[self.db2_name]
+
+    def tearDown(self):
+        super(MergeTest, self).tearDown()
+        self.client2.drop_database(self.db2_name)
+
+    def test_left_right_merge(self):
+        item_string = ''.join(random.choice(string.lowercase) for i in range(10))
+        item = {'string': item_string}
+        item_id = self.db[self.collection_name].save(item)
+
+        merge(self.client, self.client2,
+              self.db.name, self.db2.name)
+
+        assert len(list(self.db[self.collection_name].find())) == 0
+        assert len(list(self.db2[self.collection_name].find())) == 1
+
+        item_retrieved = self.db2[self.collection_name].find_one({'_id': item_id})
+        assert item_retrieved is not None
+        assert item_retrieved['string'] == item_string
+