Go mockgen, mocked function not called - go

Question

I am using Go 1.19 on a windows machine with 8 cores, operating system is Windows 10 Pro.
I used the mockgen tool to generate the mock. When I debug my test I see the mocked method is recorded when I execute the EXPECT() function.
The mocked function is called, but the test fails with 'missing call' on the mocked function.
I cannot see what I am doing wrong, can anyone please point it out ?
Directory Structure :
cmd
configure.go
configure_test.go
mocks
mock_validator.go
validator
validator.go
user
user.go
go.mod
main.go
* Contents of main.go
package main
import (
"localdev/mockexample/cmd"
)
func main() {
cmd.Configure()
}
* Contents of configure.go
package cmd
import (
"fmt"
"localdev/mockexample/user"
"os"
"localdev/mockexample/validator"
)
var (
name, password string
)
func Configure() {
name := os.Args[1]
password := os.Args[2]
user, err := validate(validator.NewValidator(name, password))
if err != nil {
fmt.Printf("%v\n", err)
return
}
fmt.Printf("Credentials are valid. Welcome: %s %s\n", user.FirstName, user.LastName)
}
func validate(validator validator.Validator) (*user.Data, error) {
user, err := validator.ValidateUser()
if err != nil {
return nil, fmt.Errorf("some thing went wrong. %v", err)
}
return user, nil
}
* Contents of validator.go
package validator
import (
"fmt"
"localdev/mockexample/user"
)
//go:generate mockgen -destination=../mocks/mock_validator.go -package=mocks localdev/mockexample/validator Validator
type Validator interface {
ValidateUser() (*user.Data, error)
}
type ValidationRequest struct {
Command string
Name string
Password string
}
func (vr ValidationRequest) ValidateUser() (*user.Data, error) {
if vr.Name == "bob" && vr.Password == "1234" {
return &user.Data{UserID: "123", UserName: "bsmith", FirstName: "Bob", LastName: "Smith"}, nil
}
return nil, fmt.Errorf("invalid credentials")
}
func NewValidator(name string, password string) Validator {
return &ValidationRequest{Name: name, Password: password}
}
* Contents of user.go
package user
type Data struct {
UserID string `json:"user_id"`
UserName string `json:"user_name"`
FirstName string `json:"first_name"`
LastName string `json:"last_name"`
}
* Contents of configure_test.go
package cmd
import (
"localdev/mockexample/mocks"
"localdev/mockexample/user"
"os"
"testing"
"github.com/golang/mock/gomock"
)
func TestConfigure(t *testing.T) {
t.Run("ConfigureWithMock", func(t *testing.T) {
os.Args[1] = "bob"
os.Args[2] = "1234"
ctrl := gomock.NewController(t)
mockValidator := mocks.NewMockValidator(ctrl)
//mockValidator.EXPECT().ValidateUser().AnyTimes() // zero more calls, so this will also pass.
userData := user.Data{UserID: "testId"}
mockValidator.EXPECT().ValidateUser().Return(&userData, nil).Times(1) //(gomock.Any(), gomock.Any()) //(&userData, nil)
Configure()
})
}
Contents of generated mock
// Code generated by MockGen. DO NOT EDIT.
// Source: localdev/mockexample/validator (interfaces: Validator)
// Package mocks is a generated GoMock package.
package mocks
import (
user "localdev/mockexample/user"
reflect "reflect"
gomock "github.com/golang/mock/gomock"
)
// MockValidator is a mock of Validator interface.
type MockValidator struct {
ctrl *gomock.Controller
recorder *MockValidatorMockRecorder
}
// MockValidatorMockRecorder is the mock recorder for MockValidator.
type MockValidatorMockRecorder struct {
mock *MockValidator
}
// NewMockValidator creates a new mock instance.
func NewMockValidator(ctrl *gomock.Controller) *MockValidator {
mock := &MockValidator{ctrl: ctrl}
mock.recorder = &MockValidatorMockRecorder{mock}
return mock
}
// EXPECT returns an object that allows the caller to indicate expected use.
func (m *MockValidator) EXPECT() *MockValidatorMockRecorder {
return m.recorder
}
// ValidateUser mocks base method.
func (m *MockValidator) ValidateUser() (*user.Data, error) {
m.ctrl.T.Helper()
ret := m.ctrl.Call(m, "ValidateUser")
ret0, _ := ret[0].(*user.Data)
ret1, _ := ret[1].(error)
return ret0, ret1
}
// ValidateUser indicates an expected call of ValidateUser.
func (mr *MockValidatorMockRecorder) ValidateUser() *gomock.Call {
mr.mock.ctrl.T.Helper()
return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ValidateUser", reflect.TypeOf((*MockValidator)(nil).ValidateUser))
}

Answer 1

The root problem is that the function Configure never uses the mock structure, so you get a missing call(s) to *mocks.MockValidator.ValidateUser() error.
In the file configure_test.go, mockValidator is simply not used at all. There must be some kind of injection of that mock in order to be called by the Configure function.
You could make the following changes to fix the test, as an example of what I'm referring to injection. Not saying this is the best approach but I'm trying to make the fewer possible changes to your code.
configure_test.go:
func TestConfigure(t *testing.T) {
t.Run("ConfigureWithMock", func(t *testing.T) {
os.Args[1] = "bob"
os.Args[2] = "1234"
ctrl := gomock.NewController(t)
mockValidator := mocks.NewMockValidator(ctrl)
//mockValidator.EXPECT().ValidateUser().AnyTimes() // zero more calls, so this will also pass.
userData := user.Data{UserID: "testId"}
mockValidator.
EXPECT().
ValidateUser("bob", "1234").
Return(&userData, nil).
Times(1) //(gomock.Any(), gomock.Any()) //(&userData, nil)
Configure(mockValidator)
})
}
configure.go
func Configure(v validator.Validator) {
name := os.Args[1]
password := os.Args[2]
user, err := v.ValidateUser(name, password)
if err != nil {
fmt.Printf("some thing went wrong. %v\n", err)
return
}
fmt.Printf("Credentials are valid. Welcome: %s %s\n", user.FirstName, user.LastName)
}
validator.go
type Validator interface {
ValidateUser(name, password string) (*user.Data, error)
}
type ValidationRequest struct {
Command string
// Name string
// Password string
}
func (vr ValidationRequest) ValidateUser(name, password string) (*user.Data, error) {
if name == "bob" && password == "1234" {
return &user.Data{UserID: "123", UserName: "bsmith", FirstName: "Bob", LastName: "Smith"}, nil
}
return nil, fmt.Errorf("invalid credentials")
}
func NewValidator() Validator {
return &ValidationRequest{}
}
Take into account that you need to generate the mock again. Hope this helps you to understand mock testing.