如何使用 gomock （或类似的）来模拟/验证对数据库的调用？

Question

转到这里，使用gorm或/映射到数据库 (PSQL)。我有以下代码：package dbstuffimport (    "errors"  "github.com/google/uuid"  "github.com/jinzhu/gorm"    _ "github.com/jinzhu/gorm/dialects/postgres")type OrderPersister struct {        db *gorm.DB}func (p *OrderPersister) GetOrder(id uuid.UUID) (*Order, error) {        ret := &Order{}        err := p.db.Table("orders").Where("order_id = ?", id).Scan(ret).Error        return ret, err}我正在尝试为它编写一个单元测试，如下所示：package dbstuffimport (    "testing"  "errors"  "github.com/stretchr/testify/assert")func TestErrInternalServerError(t *testing.T) {  // given  id := uuid.New()  op := OrderPersister{}  // when  order, err := op.GetOrder(id)  // then  assert.NotNil(t, order)  assert.NotNil(t, err)}当我运行它时，我得到无效的内存地址或 nil 指针取消引用错误，因为我没有*gorm.DB在我的OrderPersister实例上实例化设置 a。有没有一种简单的方法来模拟/存根，以便我的测试确认我们尝试查询orders表并返回或/映射结果？

Answer 1

我将使用testify包为您的代码编写单元测试。而不是使用具体类型，而是为struct*gorm.DB声明 DB 接口。OrderPersister由于我们不能在 Go 中模拟具体类型及其方法。我们需要创建一个抽象层—— interface.

63622995/db/db.go:

package db

type OrmDBWithError struct {

    OrmDB

    Error error

}

type OrmDB interface {

    Table(name string) OrmDB

    Where(query interface{}, args ...interface{}) OrmDB

    Scan(dest interface{}) *OrmDBWithError

}

63622995/main.go:

package main

import (

    "github.com/google/uuid"

    _ "github.com/jinzhu/gorm/dialects/postgres"

    "github.com/mrdulin/golang/src/stackoverflow/63622995/db"

)

type Order struct {

    order_id string

}

type OrderPersister struct {

    DB db.OrmDB

    //DB *gorm.DB

}

func (p *OrderPersister) GetOrder(id uuid.UUID) (*Order, error) {

    ret := &Order{}

    err := p.DB.Table("orders").Where("order_id = ?", id).Scan(ret).Error

    return ret, err

}

OrmDB为实现接口的 db 创建了模拟对象。然后，您可以创建此模拟 DB 对象并将其传递给OrderPersisterstruct。

63622995/mocks/db.go:

package mocks

import (

    "github.com/mrdulin/golang/src/stackoverflow/63622995/db"

    "github.com/stretchr/testify/mock"

)

type MockedOrmDB struct {

    mock.Mock

}

func (s *MockedOrmDB) Table(name string) db.OrmDB {

    args := s.Called(name)

    return args.Get(0).(db.OrmDB)

}

func (s *MockedOrmDB) Where(query interface{}, args ...interface{}) db.OrmDB {

    arguments := s.Called(query, args)

    return arguments.Get(0).(db.OrmDB)

}

func (s *MockedOrmDB) Scan(dest interface{}) *db.OrmDBWithError {

    args := s.Called(dest)

    return args.Get(0).(*db.OrmDBWithError)

}

63622995/main_test.go:

package main

import (

    "testing"

    "github.com/google/uuid"

    "github.com/mrdulin/golang/src/stackoverflow/63622995/db"

    "github.com/mrdulin/golang/src/stackoverflow/63622995/mocks"

    "github.com/stretchr/testify/assert"

    "github.com/stretchr/testify/mock"

)

func TestOrderPersister_GetOrder(t *testing.T) {

    assert := assert.New(t)

    t.Run("should get order", func(t *testing.T) {

        testDb := new(mocks.MockedOrmDB)

        id := uuid.New()

        testDb.

            On("Table", "orders").

            Return(testDb).

            On("Where", "order_id = ?", mock.Anything).

            Return(testDb).

            On("Scan", mock.Anything).Run(func(args mock.Arguments) {

            ret := args.Get(0).(*Order)

            ret.order_id = "123"

        }).

            Return(&db.OrmDBWithError{Error: nil})

        op := OrderPersister{DB: testDb}

        got, err := op.GetOrder(id)

        testDb.AssertExpectations(t)

        assert.Nil(err)

        assert.Equal(Order{order_id: "123"}, *got)

    })

    t.Run("should return error", func(t *testing.T) {

        testDb := new(mocks.MockedOrmDB)

        id := uuid.New()

        testDb.

            On("Table", "orders").

            Return(testDb).

            On("Where", "order_id = ?", mock.Anything).

            Return(testDb).

            On("Scan", mock.Anything).

            Return(&db.OrmDBWithError{Error: errors.New("network")})

        op := OrderPersister{DB: testDb}

        got, err := op.GetOrder(id)

        testDb.AssertExpectations(t)

        assert.Equal(Order{}, *got)

        assert.Equal(err.Error(), "network")

    })

}

单元测试结果：

=== RUN   TestOrderPersister_GetOrder

=== RUN   TestOrderPersister_GetOrder/should_get_order

    TestOrderPersister_GetOrder/should_get_order: main_test.go:32: PASS:    Table(string)

    TestOrderPersister_GetOrder/should_get_order: main_test.go:32: PASS:    Where(string,string)

    TestOrderPersister_GetOrder/should_get_order: main_test.go:32: PASS:    Scan(string)

=== RUN   TestOrderPersister_GetOrder/should_return_error

    TestOrderPersister_GetOrder/should_return_error: main_test.go:49: PASS: Table(string)

    TestOrderPersister_GetOrder/should_return_error: main_test.go:49: PASS: Where(string,string)

    TestOrderPersister_GetOrder/should_return_error: main_test.go:49: PASS: Scan(string)

--- PASS: TestOrderPersister_GetOrder (0.00s)

    --- PASS: TestOrderPersister_GetOrder/should_get_order (0.00s)

    --- PASS: TestOrderPersister_GetOrder/should_return_error (0.00s)

PASS

Process finished with exit code 0

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