Implementing delete-group endpoint and appropriate test case

tests/test_iam/test_iam_groups.py

@@ -182,3 +182,14 @@ def test_list_group_policies():
     conn.list_group_policies(GroupName="my-group")["PolicyNames"].should.equal(
         ["my-policy"]
     )
+
+
+@mock_iam
+def test_delete_group():
+    conn = boto3.client('iam', region_name='us-east-1')
+    conn.create_group(GroupName='my-group')
+    groups = conn.list_groups()
+    assert groups['Groups'][0]['GroupName'] == 'my-group'
+    assert len(groups['Groups']) == 1
+    conn.delete_group(GroupName='my-group')
+    conn.list_groups()['Groups'].should.be.empty