Question [Not a issue] about go-mock HOT 4 CLOSED

package mock

import (
    "errors"
    "testing"

    "gopkg.in/redis.v3"
)

type Client struct {
    base redis.Client
}

func (c *Client) ZAdd(key string, members ...redis.Z) IntCmdInterface {
    return c.base.ZAdd(key, members...)
}

func (c *Client) ZRem(key string, members ...string) IntCmdInterface {
    return c.base.ZRem(key, members...)
}

type ClientInterface interface {
    ZAdd(key string, members ...redis.Z) IntCmdInterface
    ZRem(key string, members ...string) IntCmdInterface
}

type ClientMock struct {
    Mock
}

func (m *ClientMock) ZAdd(key string, members ...redis.Z) IntCmdInterface {
    ret := m.Called(key, members)
    return ret.Get(0).(IntCmdInterface)
}

func (m *ClientMock) ZRem(key string, members ...string) IntCmdInterface {
    ret := m.Called(key, members)
    return ret.Get(0).(IntCmdInterface)
}

type IntCmdInterface interface {
    Result() (int64, error)
}

type IntCmdMock struct {
    Mock
}

func (m *IntCmdMock) Result() (int64, error) {
    ret := m.Called()
    return ret.Int64(0), ret.Error(1)
}

func TestRedis(t *testing.T) {
    client := ClientMock{}
    cmd1 := &IntCmdMock{}
    cmd2 := &IntCmdMock{}
    cmd3 := &IntCmdMock{}

    cmd1.When("Result").Return(int64(123), nil)
    cmd2.When("Result").Return(int64(456), nil)
    cmd3.When("Result").Return(int64(0), errors.New("an error"))

    client.When("ZAdd", "foo", Any).Return(cmd1)
    client.When("ZRem", "bar", Any).Return(cmd2)
    client.When("ZRem", "zar", Any).Return(cmd3)

    ret := client.ZAdd("foo", redis.Z{1.00, "member"})
    if i, err := ret.Result(); i != 123 || err != nil {
        t.Fatal("Result is not 123")
    }

    ret = client.ZRem("bar")
    if i, err := ret.Result(); i != 456 || err != nil {
        t.Fatal("Result is not 456")
    }

    ret = client.ZRem("zar")
    if i, err := ret.Result(); i != 0 || err == nil || err.Error() != "an error" {
        t.Fatal("error is not `an error`")
    }
}

func (c *Client) ZAdd(key string, members ...redis.Z) (int64, error) {
    return c.base.ZAdd(key, members...).Result()
}