Mset should fail on empty kwargs/args (#146)

* Replicates redis library error 'wrong number of arguments for 'mset' command'

Author: ojomio

mockredis/client.py

@@ -408,12 +408,15 @@ def mset(self, *args, **kwargs):
         Sets key/values based on a mapping. Mapping can be supplied as a single
         dictionary argument or as kwargs.
         """
+        mapping = kwargs
         if args:
             if len(args) != 1 or not isinstance(args[0], dict):
                 raise RedisError('MSET requires **kwargs or a single dict arg')
-            mapping = args[0]
-        else:
-            mapping = kwargs
+            mapping.update(args[0])
+
+        if len(mapping) == 0:
+            raise ResponseError("wrong number of arguments for 'mset' command")
+
         for key, value in mapping.items():
             self.set(key, value)
         return True

mockredis/tests/test_string.py

@@ -3,7 +3,11 @@
 from nose.tools import eq_, ok_
 
 from mockredis.client import get_total_milliseconds
-from mockredis.tests.fixtures import raises_response_error, setup, teardown
+from mockredis.tests.fixtures import (
+    raises_response_error,
+    setup,
+    teardown,
+)
 
 
 class TestRedisString(object):
@@ -203,7 +207,21 @@ def test_strict_setex_zero_expiration(self):
     def test_mset(self):
         ok_(self.redis.mset({"key1": "hello", "key2": ""}))
         ok_(self.redis.mset(**{"key3": "world", "key2": "there"}))
-        eq_([b"hello", b"there", b"world"], self.redis.mget("key1", "key2", "key3"))
+        ok_(self.redis.mset(
+            {"key4": "ican"}, **{"key4": "haz", "key5": "cheezburger"})
+        )
+        eq_(
+            [b"hello", b"there", b"world", b"ican", b"cheezburger"],
+            self.redis.mget("key1", "key2", "key3", "key4", "key5")
+        )
+
+    @raises_response_error
+    def test_mset_empty_kwargs(self):
+        self.redis.mset(**{})
+
+    @raises_response_error
+    def test_mset_empty_args(self):
+        self.redis.mset({})
 
     def test_msetnx(self):
         ok_(self.redis.msetnx({"key1": "hello", "key2": "there"}))