go语言中GoMock安装使用详解

安装

GoMock是一个Go框架。它与内置的测试包整合得很好,并在单元测试时提供了灵活性。正如我们所知,对具有外部资源(数据库、网络和文件)或依赖关系的代码进行单元测试总是很麻烦。

为了使用GoMock,我们需要安装gomockgithub.com/golang/mock/gomockmockgen代码生成工具github.com/golang/mock/mockgen。使用这个命令行:

go get github.com/golang/mock/gomock
go get github.com/golang/mock/mockgen

GoMock的使用遵循四个基本步骤:

  • 使用mockgen为你想模拟的接口生成一个模拟对象。
  • 在测试部分,创建一个gomock.Controller的实例,并把它传递给你的mock对象的构造函数以获得一个mock对象。
  • 在mock上调用EXPECT()来设置期望值和返回值。
  • 在模拟控制器上调用Finish()来断言模拟对象的期望。

开始

让我们创建一个这样的文件夹(本代码在 go1.16.15 版本下执行)

gomock_test
├── doer
│ └── doer.go
├── mocks
│ └── mock_doer.go
└── user
 ├── user.go
 └── user_test.go

doer/doer.go

package doer
type Doer interface {
 DoSomething(int, string) error
 SaySomething(string) string
}

那么这里是我们在模拟Doer接口时要测试的代码。

user/user.go

package user
import "gomock_test/doer"
const (
	filtered = "OK"
	unfiltered = "spam"
	Nice = "nice"
	Bad = "bad"
)
type User struct {
	// struct while mocking the doer interface
	Doer doer.Doer
}
// method Use using it
func (u *User) Use() error {
	return u.Doer.DoSomething(123, "Hello GoMock")
}
func (u *User) SaySomething(num int) string {
	if num == 3 {
	return u.Doer.SaySomething(unfiltered)
	}
	return u.Doer.SaySomething(filtered)
}
type Student struct{}
func (s *Student) DoSomething(_ int, _ string) error {
	panic("not implemented") // TODO: Implement
}
func (s *Student) SaySomething(kata string) string {
	if kata == filtered {
	return Nice
	}
	return Bad
}

我们将把Doer的模拟放在一个包mocks中。我们首先创建一个包含我们的模拟实现的目录mocks,然后在doer包上运行mockgen

mockgen -destination=../mocks/mock_doer.go -package=mocks gomock_test/doer Doer

NOTE: 在执行这步的时候,会报错:Failed to format generated source code: mocks/mock_doer.go:5:15: expected ';', found '.’ 这个时候,我们只需要将打印出来的代码复制到我们对应的文件中即可。

当有大量的接口/包需要模拟时,为每个包和接口运行mockgen是一种乌托邦。为了缓解这个问题,可以将mockgen命令与go:generate放在一起。

go:generate mockgen -destination=../mocks/mock_doer.go -package=mocks gomock_test/doer Doer

我们必须自己创建目录模拟,因为GoMock不会为我们这样做,而是会以错误退出。

  • destination=.../mocks/mock_doer.go : 把生成的mocks放在这个路径下。
  • -package=mocks : 把生成的mocks放在这个包里
  • gomock_test/doer : 为这个包生成mocks。
  • Doer : 为这个接口生成mocks(必填),因为我们需要指定哪个接口来生成mocks。(如果需要的话,可以用逗号分隔的列表来指定多个接口。例如,Doer1, Doer2)

因为我们对mockgen的调用在我们的项目中放置了一个文件mocks/mock_doer.go。这就是这样一个生成的mock实现的样子:

// Code generated by MockGen. DO NOT EDIT.
// Source: github.com/timliudream/go-test/gomock_test/doer (interfaces: Doer)
// Package github.com/timliudream/go-test/gomock_test/mocks is a generated GoMock package.
package mocks
import (
	gomock "github.com/golang/mock/gomock"
	reflect "reflect"
)
// MockDoer is a mock of Doer interface.
type MockDoer struct {
	ctrl *gomock.Controller
	recorder *MockDoerMockRecorder
}
// MockDoerMockRecorder is the mock recorder for MockDoer.
type MockDoerMockRecorder struct {
	mock *MockDoer
}
// NewMockDoer creates a new mock instance.
func NewMockDoer(ctrl *gomock.Controller) *MockDoer {
	mock := &MockDoer{ctrl: ctrl}
	mock.recorder = &MockDoerMockRecorder{mock}
	return mock
}
// EXPECT returns an object that allows the caller to indicate expected use.
func (m *MockDoer) EXPECT() *MockDoerMockRecorder {
	return m.recorder
}
// DoSomething mocks base method.
func (m *MockDoer) DoSomething(arg0 int, arg1 string) error {
	m.ctrl.T.Helper()
	ret := m.ctrl.Call(m, "DoSomething", arg0, arg1)
	ret0, _ := ret[0].(error)
	return ret0
}
// DoSomething indicates an expected call of DoSomething.
func (mr *MockDoerMockRecorder) DoSomething(arg0, arg1 interface{}) *gomock.Call {
	mr.mock.ctrl.T.Helper()
	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DoSomething", reflect.TypeOf((*MockDoer)(nil).DoSomething), arg0, arg1)
}
// SaySomething mocks base method.
func (m *MockDoer) SaySomething(arg0 string) string {
	m.ctrl.T.Helper()
	ret := m.ctrl.Call(m, "SaySomething", arg0)
	ret0, _ := ret[0].(string)
	return ret0
}
// SaySomething indicates an expected call of SaySomething.
func (mr *MockDoerMockRecorder) SaySomething(arg0 interface{}) *gomock.Call {
	mr.mock.ctrl.T.Helper()
	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SaySomething", reflect.TypeOf((*MockDoer)(nil).SaySomething), arg0)
}

接下来,我们在测试中定义一个模拟控制器。一个模拟控制器负责跟踪和断言其相关模拟对象的期望。我们可以通过传递一个*testing.T类型的值给它的构造函数来获得一个模拟控制器,并使用它来构造一个Doer接口的模拟对象。

//core of gomock
mockCtrl := gomock.NewController(t)
//used to trigger final assertions. if its ignored, mocking assertions will never fail
defer mockCtrl.Finish()
// create a new mock object, passing the controller instance as parameter
// for a newly created mock object it will accept any input and outpuite
// need to define its behavior with the method expect
mockDoer := mocks.NewMockDoer(mockCtrl)

使用参数匹配器

在GoMock中,一个参数可以被期望有一个固定的值,也可以被期望与一个谓词(称为匹配器)相匹配。匹配器用于表示被模拟方法的预期参数范围。下列匹配器在Gomock中被预先定义了:

  • gomock.Any() : 匹配任何值(任何类型)。
  • gomock.Eq(x) : 使用反射来匹配与x深度相等的值。
  • gomock.Nil() : 匹配nil

user/user_test.go

package user
import (
	"fmt"
	"github.com/golang/mock/gomock"
	"gomock_test/mocks"
	"testing"
)
func TestUse(t *testing.T) {
	//core of gomock
	mockCtrl := gomock.NewController(t)
	//used to trigger final assertions. if its ignored, mocking assertions will never fail
	defer mockCtrl.Finish()
	// create a new mock object, passing the controller instance as parameter
	// for a newly created mock object it will accept any input and outpuite
	// need to define its behavior with the method expect
	mockDoer := mocks.NewMockDoer(mockCtrl)
	testUser := &User{Doer: mockDoer}
	//
	// Expect Do to be called once with 123 and "Hello GoMock" as parameters, and return nil from the mocked call.
	mockDoer.EXPECT().DoSomething(123, "Hello GoMock").Return(nil).Times(1)
	fmt.Println(testUser.Use())
	fmt.Println()
}
func TestUser_SaySomething(t *testing.T) {
	mockCtrl := gomock.NewController(t)
	defer mockCtrl.Finish()
	mockDoer := mocks.NewMockDoer(mockCtrl)
	user := User{
	Doer: mockDoer,
	}
	type args struct {
	num int
	}
	tests := []struct {
	name string
	args args
	want string
	expect func()
	wantErr bool
	}{
	{
	name: "Positive test case 1",
	expect: func() {
	mockDoer.EXPECT().SaySomething("spam").Return("bad")
	},
	args: args{num: 3},
	wantErr: false,
	want: "bad",
	},
	}
	for _, tt := range tests {
	t.Run(tt.name, func(t *testing.T) {
	tt.expect()
	if got := user.SaySomething(tt.args.num); (got != tt.want) != tt.wantErr {
	fmt.Println("gott :", got)
	t.Errorf("User.SaySomething() = %v, want %v", got, tt.want)
	}
	})
	}
}

而单元测试的结果将是这样的:

=== RUN   TestUser_SaySomething
=== RUN   TestUser_SaySomething/Positive_test_case_1
--- PASS: TestUser_SaySomething (0.00s)
    --- PASS: TestUser_SaySomething/Positive_test_case_1 (0.00s)
PASS
ok      github.com/tokopedia/go_learning/udemy/pzn/gomock_test/user     1.100s

经验之谈

可以在不调用外部依赖的情况下进行单元测试。使用mocking框架可以在很多方面帮助我们,建立干净和轻量级的单元测试。与接口和依赖注入相结合。

作者:洛天枫

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