How to Write Unit Tests for GORM Repository Method with gomock?

I am trying to write unit tests for a GORM repository method using gomock to mock database interactions. However, I’m running into issues with nil pointer dereference errors. Below are the relevant parts of my code:

Repository Code:

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<code>package repositories
import (
"github.com/CAVAh/api-tech-challenge/src/core/domain/entities"
"github.com/CAVAh/api-tech-challenge/src/infra/db/database"
"github.com/CAVAh/api-tech-challenge/src/infra/db/models"
)
type CustomerRepository struct {
DB database.Database
}
func (r CustomerRepository) FindFirstByCpf(entity *entities.Customer) (*entities.Customer, error) {
var customer models.Customer
db := r.DB.Where("cpf = ?", entity.CPF)
err := db.First(&customer).Error
if err != nil {
return nil, err
}
result := customer.ToDomain()
return &result, nil
}
</code>
<code>package repositories import ( "github.com/CAVAh/api-tech-challenge/src/core/domain/entities" "github.com/CAVAh/api-tech-challenge/src/infra/db/database" "github.com/CAVAh/api-tech-challenge/src/infra/db/models" ) type CustomerRepository struct { DB database.Database } func (r CustomerRepository) FindFirstByCpf(entity *entities.Customer) (*entities.Customer, error) { var customer models.Customer db := r.DB.Where("cpf = ?", entity.CPF) err := db.First(&customer).Error if err != nil { return nil, err } result := customer.ToDomain() return &result, nil } </code>
package repositories

import (
    "github.com/CAVAh/api-tech-challenge/src/core/domain/entities"
    "github.com/CAVAh/api-tech-challenge/src/infra/db/database"
    "github.com/CAVAh/api-tech-challenge/src/infra/db/models"
)

type CustomerRepository struct {
    DB database.Database
}

func (r CustomerRepository) FindFirstByCpf(entity *entities.Customer) (*entities.Customer, error) {
    var customer models.Customer

    db := r.DB.Where("cpf = ?", entity.CPF)
    err := db.First(&customer).Error

    if err != nil {
        return nil, err
    }

    result := customer.ToDomain()

    return &result, nil
}

Database Interface:

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<code>package database
import (
"gorm.io/gorm"
)
type Database interface {
Create(data interface{}) error
Where(query interface{}, args ...interface{}) *gorm.DB
First(dest interface{}, conds ...interface{}) error
}
type RealDatabase struct {
db *gorm.DB
}
func (rdb *RealDatabase) Create(data interface{}) error {
return rdb.db.Create(data).Error
}
func (rdb *RealDatabase) Where(query interface{}, args ...interface{}) *gorm.DB {
return rdb.db.Where(query, args...)
}
func (rdb *RealDatabase) First(dest interface{}, conds ...interface{}) error {
return rdb.db.First(dest, conds...).Error
}
</code>
<code>package database import ( "gorm.io/gorm" ) type Database interface { Create(data interface{}) error Where(query interface{}, args ...interface{}) *gorm.DB First(dest interface{}, conds ...interface{}) error } type RealDatabase struct { db *gorm.DB } func (rdb *RealDatabase) Create(data interface{}) error { return rdb.db.Create(data).Error } func (rdb *RealDatabase) Where(query interface{}, args ...interface{}) *gorm.DB { return rdb.db.Where(query, args...) } func (rdb *RealDatabase) First(dest interface{}, conds ...interface{}) error { return rdb.db.First(dest, conds...).Error } </code>
package database

import (
    "gorm.io/gorm"
)

type Database interface {
    Create(data interface{}) error
    Where(query interface{}, args ...interface{}) *gorm.DB
    First(dest interface{}, conds ...interface{}) error
}

type RealDatabase struct {
    db *gorm.DB
}

func (rdb *RealDatabase) Create(data interface{}) error {
    return rdb.db.Create(data).Error
}

func (rdb *RealDatabase) Where(query interface{}, args ...interface{}) *gorm.DB {
    return rdb.db.Where(query, args...)
}

func (rdb *RealDatabase) First(dest interface{}, conds ...interface{}) error {
    return rdb.db.First(dest, conds...).Error
}

Unit Test Code:

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<code>package repositories
import (
"testing"
"github.com/CAVAh/api-tech-challenge/src/core/domain/entities"
"github.com/CAVAh/api-tech-challenge/src/infra/db/models"
gomock "go.uber.org/mock/gomock"
"github.com/stretchr/testify/assert"
)
func TestFindFirstByCpf_Success(t *testing.T) {
ctrl := gomock.NewController(t)
defer ctrl.Finish()
mockDB := mocks.NewMockDatabase(ctrl)
repo := CustomerRepository{DB: mockDB}
entity := &entities.Customer{CPF: "12345678901"}
customerModel := models.Customer{
Name: "John Doe",
CPF: "12345678901",
Email: "[email protected]",
}
// Mock for returning the correct instance of gorm.DB
mockGormDB := &gorm.DB{}
mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockGormDB).Times(1)
mockDB.EXPECT().First(gomock.Any()).DoAndReturn(func(dest interface{}) *gorm.DB {
*dest.(*models.Customer) = customerModel
return &gorm.DB{}
}).Times(1)
result, err := repo.FindFirstByCpf(entity)
assert.NoError(t, err)
assert.NotNil(t, result)
assert.Equal(t, "John Doe", result.Name)
assert.Equal(t, "12345678901", result.CPF)
assert.Equal(t, "[email protected]", result.Email)
}
</code>
<code>package repositories import ( "testing" "github.com/CAVAh/api-tech-challenge/src/core/domain/entities" "github.com/CAVAh/api-tech-challenge/src/infra/db/models" gomock "go.uber.org/mock/gomock" "github.com/stretchr/testify/assert" ) func TestFindFirstByCpf_Success(t *testing.T) { ctrl := gomock.NewController(t) defer ctrl.Finish() mockDB := mocks.NewMockDatabase(ctrl) repo := CustomerRepository{DB: mockDB} entity := &entities.Customer{CPF: "12345678901"} customerModel := models.Customer{ Name: "John Doe", CPF: "12345678901", Email: "[email protected]", } // Mock for returning the correct instance of gorm.DB mockGormDB := &gorm.DB{} mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockGormDB).Times(1) mockDB.EXPECT().First(gomock.Any()).DoAndReturn(func(dest interface{}) *gorm.DB { *dest.(*models.Customer) = customerModel return &gorm.DB{} }).Times(1) result, err := repo.FindFirstByCpf(entity) assert.NoError(t, err) assert.NotNil(t, result) assert.Equal(t, "John Doe", result.Name) assert.Equal(t, "12345678901", result.CPF) assert.Equal(t, "[email protected]", result.Email) } </code>
package repositories

import (
    "testing"

    "github.com/CAVAh/api-tech-challenge/src/core/domain/entities"
    "github.com/CAVAh/api-tech-challenge/src/infra/db/models"
    gomock "go.uber.org/mock/gomock"
    "github.com/stretchr/testify/assert"
)

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

    mockDB := mocks.NewMockDatabase(ctrl)
    repo := CustomerRepository{DB: mockDB}

    entity := &entities.Customer{CPF: "12345678901"}
    customerModel := models.Customer{
        Name:  "John Doe",
        CPF:   "12345678901",
        Email: "[email protected]",
    }

    // Mock for returning the correct instance of gorm.DB
    mockGormDB := &gorm.DB{}
    mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockGormDB).Times(1)
    mockDB.EXPECT().First(gomock.Any()).DoAndReturn(func(dest interface{}) *gorm.DB {
        *dest.(*models.Customer) = customerModel
        return &gorm.DB{}
    }).Times(1)

    result, err := repo.FindFirstByCpf(entity)
    assert.NoError(t, err)
    assert.NotNil(t, result)
    assert.Equal(t, "John Doe", result.Name)
    assert.Equal(t, "12345678901", result.CPF)
    assert.Equal(t, "[email protected]", result.Email)
}

Error Message:

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<code>--- FAIL: TestFindFirstByCpf_Success (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
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=0x60 pc=0x5c06df]
goroutine 9 [running]:
testing.tRunner.func1.2({0x6a8860, 0x94d7c0})
/usr/local/go/src/testing/testing.go:1631 +0x24a
testing.tRunner.func1()
/usr/local/go/src/testing/testing.go:1634 +0x377
panic({0x6a8860?, 0x94d7c0?})
/usr/local/go/src/runtime/panic.go:770 +0x132
go.uber.org/mock/gomock.(*Controller).finish(0xc0001f5950, 0x0, {0x6a8860, 0x94d7c0})
/home/cava/go/pkg/mod/go.uber.org/[email protected]/gomock/controller.go:270 +0x25f
go.uber.org/mock/gomock.(*Controller).Finish(0xc0001f5950)
/home/cava/go/pkg/mod/go.uber.org/[email protected]/gomock/controller.go:243 +0x37
panic({0x6a8860?, 0x94d7c0?})
/usr/local/go/src/runtime/panic.go:770 +0x132
gorm.io/gorm.(*Statement).AddClause(0x0, {0x7837a0, 0xc0001abe70})
/home/cava/go/pkg/mod/gorm.io/[email protected]/statement.go:269 +0x7f
gorm.io/gorm.(*DB).Limit(0xc0001f59b0, 0x1)
/home/cava/go/pkg/mod/gorm.io/[email protected]/chainable_api.go:332 +0x85
gorm.io/gorm.(*DB).First(0xc0001abd80?, {0x6a2ec0, 0xc0001fe750}, {0x0, 0x0, 0x0})
/home/cava/go/pkg/mod/gorm.io/[email protected]/finisher_api.go:119 +0x4c
github.com/CAVAh/api-tech-challenge/src/infra/db/repositories.CustomerRepository.FindFirstByCpf({{0x783530?, 0xc0001abd80?}}, 0xc0000a4ee8)
/mnt/c/Users/Cava/Documents/code/customer-service/src/infra/db/repositories/customer_repository.go:40 +0x115
github.com/CAVAh/api-tech-challenge/src/infra/db/repositories.TestFindFirstByCpf_Success(0xc0000d5520)
/mnt/c/Users/Cava/Documents/code/customer-service/src/infra/db/repositories/customer_repository_test.go:101 +0x37a
testing.tRunner(0xc0000d5520, 0x7315f0)
/usr/local/go/src/testing/testing.go:1689 +0xfb
created by testing.(*T).Run in goroutine 1
/usr/local/go/src/testing/testing.go:1742 +0x390
FAIL github.com/CAVAh/api-tech-challenge/src/infra/db/repositories 0.008s
</code>
<code>--- FAIL: TestFindFirstByCpf_Success (0.00s) panic: runtime error: invalid memory address or nil pointer dereference [recovered] 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=0x60 pc=0x5c06df] goroutine 9 [running]: testing.tRunner.func1.2({0x6a8860, 0x94d7c0}) /usr/local/go/src/testing/testing.go:1631 +0x24a testing.tRunner.func1() /usr/local/go/src/testing/testing.go:1634 +0x377 panic({0x6a8860?, 0x94d7c0?}) /usr/local/go/src/runtime/panic.go:770 +0x132 go.uber.org/mock/gomock.(*Controller).finish(0xc0001f5950, 0x0, {0x6a8860, 0x94d7c0}) /home/cava/go/pkg/mod/go.uber.org/[email protected]/gomock/controller.go:270 +0x25f go.uber.org/mock/gomock.(*Controller).Finish(0xc0001f5950) /home/cava/go/pkg/mod/go.uber.org/[email protected]/gomock/controller.go:243 +0x37 panic({0x6a8860?, 0x94d7c0?}) /usr/local/go/src/runtime/panic.go:770 +0x132 gorm.io/gorm.(*Statement).AddClause(0x0, {0x7837a0, 0xc0001abe70}) /home/cava/go/pkg/mod/gorm.io/[email protected]/statement.go:269 +0x7f gorm.io/gorm.(*DB).Limit(0xc0001f59b0, 0x1) /home/cava/go/pkg/mod/gorm.io/[email protected]/chainable_api.go:332 +0x85 gorm.io/gorm.(*DB).First(0xc0001abd80?, {0x6a2ec0, 0xc0001fe750}, {0x0, 0x0, 0x0}) /home/cava/go/pkg/mod/gorm.io/[email protected]/finisher_api.go:119 +0x4c github.com/CAVAh/api-tech-challenge/src/infra/db/repositories.CustomerRepository.FindFirstByCpf({{0x783530?, 0xc0001abd80?}}, 0xc0000a4ee8) /mnt/c/Users/Cava/Documents/code/customer-service/src/infra/db/repositories/customer_repository.go:40 +0x115 github.com/CAVAh/api-tech-challenge/src/infra/db/repositories.TestFindFirstByCpf_Success(0xc0000d5520) /mnt/c/Users/Cava/Documents/code/customer-service/src/infra/db/repositories/customer_repository_test.go:101 +0x37a testing.tRunner(0xc0000d5520, 0x7315f0) /usr/local/go/src/testing/testing.go:1689 +0xfb created by testing.(*T).Run in goroutine 1 /usr/local/go/src/testing/testing.go:1742 +0x390 FAIL github.com/CAVAh/api-tech-challenge/src/infra/db/repositories 0.008s </code>
--- FAIL: TestFindFirstByCpf_Success (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
        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=0x60 pc=0x5c06df]

goroutine 9 [running]:
testing.tRunner.func1.2({0x6a8860, 0x94d7c0})
        /usr/local/go/src/testing/testing.go:1631 +0x24a
testing.tRunner.func1()
        /usr/local/go/src/testing/testing.go:1634 +0x377
panic({0x6a8860?, 0x94d7c0?})
        /usr/local/go/src/runtime/panic.go:770 +0x132
go.uber.org/mock/gomock.(*Controller).finish(0xc0001f5950, 0x0, {0x6a8860, 0x94d7c0})
        /home/cava/go/pkg/mod/go.uber.org/[email protected]/gomock/controller.go:270 +0x25f
go.uber.org/mock/gomock.(*Controller).Finish(0xc0001f5950)
        /home/cava/go/pkg/mod/go.uber.org/[email protected]/gomock/controller.go:243 +0x37
panic({0x6a8860?, 0x94d7c0?})
        /usr/local/go/src/runtime/panic.go:770 +0x132
gorm.io/gorm.(*Statement).AddClause(0x0, {0x7837a0, 0xc0001abe70})
        /home/cava/go/pkg/mod/gorm.io/[email protected]/statement.go:269 +0x7f
gorm.io/gorm.(*DB).Limit(0xc0001f59b0, 0x1)
        /home/cava/go/pkg/mod/gorm.io/[email protected]/chainable_api.go:332 +0x85
gorm.io/gorm.(*DB).First(0xc0001abd80?, {0x6a2ec0, 0xc0001fe750}, {0x0, 0x0, 0x0})
        /home/cava/go/pkg/mod/gorm.io/[email protected]/finisher_api.go:119 +0x4c
github.com/CAVAh/api-tech-challenge/src/infra/db/repositories.CustomerRepository.FindFirstByCpf({{0x783530?, 0xc0001abd80?}}, 0xc0000a4ee8)
        /mnt/c/Users/Cava/Documents/code/customer-service/src/infra/db/repositories/customer_repository.go:40 +0x115
github.com/CAVAh/api-tech-challenge/src/infra/db/repositories.TestFindFirstByCpf_Success(0xc0000d5520)
        /mnt/c/Users/Cava/Documents/code/customer-service/src/infra/db/repositories/customer_repository_test.go:101 +0x37a
testing.tRunner(0xc0000d5520, 0x7315f0)
        /usr/local/go/src/testing/testing.go:1689 +0xfb
created by testing.(*T).Run in goroutine 1
        /usr/local/go/src/testing/testing.go:1742 +0x390
FAIL    github.com/CAVAh/api-tech-challenge/src/infra/db/repositories   0.008s

I’ve tried several different approaches, like:

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<code>mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(&gorm.DB{Error: nil}).Times(1)
// AND
mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockDB).Times(1)
// AND
mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockDB.Where("cpf = ?", entity.CPF))
</code>
<code>mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(&gorm.DB{Error: nil}).Times(1) // AND mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockDB).Times(1) // AND mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockDB.Where("cpf = ?", entity.CPF)) </code>
mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(&gorm.DB{Error: nil}).Times(1)
// AND
mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockDB).Times(1)
// AND
mockDB.EXPECT().Where("cpf = ?", entity.CPF).Return(mockDB.Where("cpf = ?", entity.CPF))

but I keep encountering this nil pointer dereference error. What am I doing wrong? How can I correctly mock the GORM database interactions to test this repository method?

Any help would be greatly appreciated!

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Trang chủ Giới thiệu Sinh nhật bé trai Sinh nhật bé gái Tổ chức sự kiện Biểu diễn giải trí Dịch vụ khác Trang trí tiệc cưới Tổ chức khai trương Tư vấn dịch vụ Thư viện ảnh Tin tức - sự kiện Liên hệ Chú hề sinh nhật Trang trí YEAR END PARTY công ty Trang trí tất niên cuối năm Trang trí tất niên xu hướng mới nhất Trang trí sinh nhật bé trai Hải Đăng Trang trí sinh nhật bé Khánh Vân Trang trí sinh nhật Bích Ngân Trang trí sinh nhật bé Thanh Trang Thuê ông già Noel phát quà Biểu diễn xiếc khỉ Xiếc quay đĩa
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