Mock Interface in Golang

1-blogs-serivces-dependency-graph

                                                      +-------------------------+
                                                      |                         |
                                                      |                         |
                  +---------------------+      +----->|        jekyll           |
                  |                     |      |      |                         |
                  |                     |      |      +-------------------------+
                  |     Service         +------+
                  |                     |
                  |                     +------+      +-------------------------+
                  +---------------------+      |      |                         |
                                               |      |                         |
                                               +----->|        wordpress        |
                                                      |                         |
                                                      +-------------------------+

2_blog.go

package service

type Post struct {}

type Blog interface {
	ListPosts() []Post
}

type jekyll struct {}

func (b *jekyll) ListPosts() []Post {
 	return []Post{}
}

type wordpress struct{}

func (b *wordpress) ListPosts() []Post {
	return []Post{}
}

3_service.go

package service

type service struct {
    blog Blog
}

func NewService(b Blog) {
    return &service{
        blog: b,
    }
}

func (s *service) ListPosts() []Post {
    return s.blog.ListPosts()
}

4_blog_test.go

package service

func TestJekyllListPosts(t *testing.T) {
    blog := &jekyll{}
    assert.Equal(t, []Post{}, blog.ListPosts())
}

func TestWordpressListPosts(t * testing.T) {
    blog := &wordpress{}
    assert.Equal(t, []Post{}, blog.ListPosts())
}

5_mock_blog.go

// Code generated by MockGen. DO NOT EDIT.
// Source: blog.go

// Package mock_service is a generated GoMock package.
package mock_service

import (
	gomock "github.com/golang/mock/gomock"
	reflect "reflect"
)

// MockBlog is a mock of Blog interface
type MockBlog struct {
	ctrl     *gomock.Controller
	recorder *MockBlogMockRecorder
}

// MockBlogMockRecorder is the mock recorder for MockBlog
type MockBlogMockRecorder struct {
	mock *MockBlog
}

// NewMockBlog creates a new mock instance
func NewMockBlog(ctrl *gomock.Controller) *MockBlog {
	mock := &MockBlog{ctrl: ctrl}
	mock.recorder = &MockBlogMockRecorder{mock}
	return mock
}

// EXPECT returns an object that allows the caller to indicate expected use
func (m *MockBlog) EXPECT() *MockBlogMockRecorder {
	return m.recorder
}

// ListPosts mocks base method
func (m *MockBlog) ListPosts() []Post {
	m.ctrl.T.Helper()
	ret := m.ctrl.Call(m, "ListPosts")
	ret0, _ := ret[0].([]Post)
	return ret0
}

// ListPosts indicates an expected call of ListPosts
func (mr *MockBlogMockRecorder) ListPosts() *gomock.Call {
	mr.mock.ctrl.T.Helper()
	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ListPosts", reflect.TypeOf((*MockBlog)(nil).ListPosts))
}

6_service_test.go

package service

import (
	"github.com/golang/mock/gomock"
	"github.com/stretchr/testify/assert"
 	"xxxx/mock_service"
)

func TestListPosts(t *testing.T) {
	ctrl := gomock.NewController(t)
	defer ctrl.Finish()

 	mockBlog := mock_service.NewMockBlog(ctrl)
 	mockBlog.EXPECT().ListPosts().Return([]Post{})
  
 	service := NewService(mockBlog)
  
 	assert.Equal(t, []Post{}, service.ListPosts())
}

mockgen -source=pkg/service/blog.go > test/mocks/mock_blog.go

type Scheduler interface{}
type scheduler struct{}

func NewScheduler() Scheduler {
}