Fix sendmany optarg parsing and add tests.

jsoncmd.go

@@ -5110,7 +5110,7 @@ func NewSendManyCmd(id interface{}, fromaccount string, amounts map[string]int64
 		minconf = m
 	}
 	if len(optArgs) > 1 {
-		c, ok := optArgs[0].(string)
+		c, ok := optArgs[1].(string)
 		if !ok {
 			return nil, errors.New("second optional parameter comment is not a string")
 		}

jsoncmd_test.go

@@ -933,6 +933,55 @@ var jsoncmdtests = []struct {
 			CommentTo:   "comment to",
 		},
 	},
+	{
+		name: "basic sendmany",
+		f: func() (Cmd, error) {
+			pairs := map[string]int64{
+				"address A": 1000,
+				"address B": 2000,
+				"address C": 3000,
+			}
+			return NewSendManyCmd(float64(1),
+				"account",
+				pairs)
+		},
+		result: &SendManyCmd{
+			id:          float64(1),
+			FromAccount: "account",
+			Amounts: map[string]int64{
+				"address A": 1000,
+				"address B": 2000,
+				"address C": 3000,
+			},
+			MinConf: 1, // the default
+		},
+	},
+	{
+		name: "sendmany + options",
+		f: func() (Cmd, error) {
+			pairs := map[string]int64{
+				"address A": 1000,
+				"address B": 2000,
+				"address C": 3000,
+			}
+			return NewSendManyCmd(float64(1),
+				"account",
+				pairs,
+				10,
+				"comment")
+		},
+		result: &SendManyCmd{
+			id:          float64(1),
+			FromAccount: "account",
+			Amounts: map[string]int64{
+				"address A": 1000,
+				"address B": 2000,
+				"address C": 3000,
+			},
+			MinConf: 10,
+			Comment: "comment",
+		},
+	},
 	{
 		name: "basic sendrawtransaction",
 		f: func() (Cmd, error) {