使用 go-sqlmock 创建 gorm 数据库时遇到运行时错误

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摘要

我正在尝试将 go-sqlmock 与 gorm 一起使用进行测试。我想为初始数据库迁移编写一个测试，但我遇到了 panic: 运行时错误: 无效的内存地址或 nil 指针取消引用 并且我一直无法找出原因。从错误堆栈来看，我认为是这个语句做到了这一点：db.automigrate(&models.user{})。我不知道为什么，因为据称此时 db 已成功启动，并且 models.user 被定义并实例化为 db.automigrate 的参数。我感觉错误出在 mocks.newdatabase 函数中，但我不知所措。

不确定是否有人有时间或意愿了解相关代码并帮助我？我已在代码中注意到发生故障的位置（它们位于最后两个代码块中）。如果有任何其他背景信息有帮助，请告诉我。

相关代码

project/src/models/models.go

package models

import (
    "time"

    "github.com/google/uuid"
    "gorm.io/gorm"
)

type base struct {
    id        uuid.uuid      `json:"-" gorm:"primarykey;type:uuid;not null"`
    createdat time.time      `json:"-" gorm:"autocreatetime"`
    updatedat time.time      `json:"-" gorm:"autoupdatetime"`
    deletedat gorm.deletedat `json:"-" gorm:"index"`
}

type user struct {
    base
    name     string `json:"-"`
    email    string `json:"-" gorm:"unique_index:user_email_index"`
    password string `json:"-" gorm:"size:72"`
}

project/src/mocks/database.go

package mocks

import (
    "project/src/models"
    "log"

    "github.com/data-dog/go-sqlmock"
    "gorm.io/driver/mysql"
    "gorm.io/gorm"
)

func newdatabase() (*gorm.db, sqlmock.sqlmock) {

    // get db and mock
    sqldb, mock, err := sqlmock.new(
        sqlmock.querymatcheroption(sqlmock.querymatcherregexp),
    )
    if err != nil {
        log.fatalf("[sqlmock new] %s", err)
    }
    defer sqldb.close()

    // create dialector
    dialector := mysql.new(mysql.config{
        conn: sqldb,
    drivername: "mysql",
    })

    // a select version() query will be run when gorm opens the database
    // so we need to expect that here
    columns := []string{"version"}
    mock.expectquery("select version()").withargs().willreturnrows(
    mock.newrows(columns).fromcsvstring("1"),
    )

    // open the database
    db, err := gorm.open(dialector, &gorm.config{ preparestmt: true })
    if err != nil {
        log.fatalf("[gorm open] %s", err)
    }

  return db, mock
}

project/src/database/init.go

package database

import (
    "project/src/models"

    "gorm.io/gorm"
)

// init auto-migrates the db.
func init(db *gorm.db) {
    // migrate the schema
    // this panics with
    // panic: runtime error: invalid memory address or nil pointer dereference
    // user is defined and instantiated here
    db.automigrate(&models.user{})
}

现在测试：

project/src/database/init_test.go

package database

import (
    "project/src/mocks"
    "testing"
)

func testinitmigratesdb(t *testing.t) {
    db, mock := mocks.newdatabase()
    mock.expectexec("create table users(.*)")
    mock.expectcommit()
    
    // fails here
    init(db)
}

还有日志

Running tool: /usr/local/go/bin/go test -timeout 30s -run ^TestInitMigratesDB$ project/src/database

--- FAIL: TestInitMigratesDB (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference
    panic: runtime error: invalid memory address or nil pointer dereference [recovered]
    panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x11ce22e]

goroutine 35 [running]:
testing.tRunner.func1.2({0x1505320, 0x19bfb00})
    /usr/local/go/src/testing/testing.go:1209 +0x24e
testing.tRunner.func1()
    /usr/local/go/src/testing/testing.go:1212 +0x218
panic({0x1505320, 0x19bfb00})
    /usr/local/go/src/runtime/panic.go:1038 +0x215
database/sql.(*Rows).close(0x0, {0x0, 0x0})
    /usr/local/go/src/database/sql/sql.go:3267 +0x8e
database/sql.(*Rows).Close(0x1e)
    /usr/local/go/src/database/sql/sql.go:3263 +0x1d
panic({0x1505320, 0x19bfb00})
    /usr/local/go/src/runtime/panic.go:1038 +0x215
database/sql.(*Rows).Next(0x0)
    /usr/local/go/src/database/sql/sql.go:2944 +0x27
database/sql.(*Row).Scan(0xc0000afbd8, {0xc0000efb38, 0x11, 0x1})
    /usr/local/go/src/database/sql/sql.go:3333 +0xb4
gorm.io/gorm/migrator.Migrator.CurrentDatabase({{0x0, 0xc000483350, {0x1659c58, 0xc00041a0f0}}})
    /go/pkg/mod/gorm.io/[email protected]/migrator/migrator.go:673 +0x8d
gorm.io/gorm/migrator.Migrator.HasTable.func1(0xc0000f8380)
    /go/pkg/mod/gorm.io/[email protected]/migrator/migrator.go:265 +0x51
gorm.io/gorm/migrator.Migrator.RunWithValue({{0x80, 0xc000483260, {0x1659c58, 0xc00041a0f0}}}, {0x1512320, 0xc0004fe2a0}, 0xc0000efcb8)
    /go/pkg/mod/gorm.io/[email protected]/migrator/migrator.go:50 +0x126
gorm.io/gorm/migrator.Migrator.HasTable({{0x0, 0xc000483260, {0x1659c58, 0xc00041a0f0}}}, {0x1512320, 0xc0004fe2a0})
    /go/pkg/mod/gorm.io/[email protected]/migrator/migrator.go:264 +0xe8
gorm.io/gorm/migrator.Migrator.AutoMigrate({{0x0, 0xc000426f90, {0x1659c58, 0xc00041a0f0}}}, {0xc00040f690, 0x0, 0x0})
    /go/pkg/mod/gorm.io/[email protected]/migrator/migrator.go:92 +0x127
gorm.io/gorm.(*DB).AutoMigrate(0x151a800, {0xc00040f690, 0x1, 0x1})
    /go/pkg/mod/gorm.io/[email protected]/migrator.go:26 +0x43
project/src/database.Init(0xc00041c230)
    /Projects/project/src/database/init.go:12 +0x7b
project/src/database.TestInitMigratesDB(0x0)
    /Projects/project/src/database/init_test.go:12 +0x5a
testing.tRunner(0xc0003a21a0, 0x15b5328)
    /usr/local/go/src/testing/testing.go:1259 +0x102
created by testing.(*T).Run
    /usr/local/go/src/testing/testing.go:1306 +0x35a
FAIL    project/src/database    0.276s
FAIL

正确答案

想通了。这是一个配置选项：&gorm.Config{PrepareStmt: true}。虽然这在生产中有效，但它不适用于 sqlmock。通过将其更改为：&gorm.Config{} 来修复此问题。

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