cannot use mockDB (variable of type *MockDB) as *gorm.DB value in struct literal

I created a get function for get exercises from the postgres db. And I wrote mock testing but I got this error from the struct how can I fix it?

I used Handler struct It has *gorm.DB struct.

error:

cannot use mockDB (variable of type *MockDB) as *gorm.DB value in struct literal

// router
package exercises
import (
"github.com/gin-gonic/gin"
"gorm.io/gorm"
)
type Handlers struct {
DB *gorm.DB
}
func RegisterRoutes(router *gin.Engine, db *gorm.DB) {
h := &Handlers{
DB: db,
}
routes := router.Group("/exercises")
routes.POST("/", h.AddExercise)
routes.GET("/", h.GetExercises)
routes.GET("/:id", h.GetExercise)
routes.PUT("/:id", h.UpdateExercise)
routes.DELETE("/:id", h.DeleteExercise)
}

// test
package exercises
import (
"net/http"
"net/http/httptest"
"testing"
"github.com/gin-gonic/gin"
"github.com/kayraberktuncer/sports-planner/pkg/common/models"
"github.com/stretchr/testify/mock"
"gorm.io/gorm"
)
type MockDB struct {
mock.Mock
}
func (m *MockDB) Find(value interface{}) *gorm.DB {
args := m.Called(value)
return args.Get(0).(*gorm.DB)
}
func (m *MockDB) Error() error {
args := m.Called()
return args.Error(0)
}
func TestGetExercises(t *testing.T) {
// Setup mock DB
mockDB := new(MockDB)
mockDB.On("Find", &[]models.Exercise{}).Return(mockDB).Once()
// Setup Gin router
router := gin.New()
router.GET("/", func(c *gin.Context) {
handlers := &Handlers{DB: mockDB} // error
handlers.GetExercises(c)
})
// Perform request
w := httptest.NewRecorder()
req, _ := http.NewRequest("GET", "/", nil)
router.ServeHTTP(w, req)
// Assert response
if w.Code != http.StatusOK {
t.Errorf("Expected status code %d, got %d", http.StatusOK, w.Code)
}
// Assert mock DB was called correctly
mockDB.AssertExpectations(t)
}

I wanted to made mock testing with my handler struct

MockDB and gorm's DB are two different structs and you cannot use them interchangeably. They can be used in the same place if they implement the same interface. For example:

// router
package exercises
import (
"github.com/gin-gonic/gin"
"gorm.io/gorm"
)
// this interface will be implemented by gorm.DB struct
type Store interface {
Create(value interface{}) *gorm.DB
First(out interface{}, where ...interface{}) *gorm.DB
Model(value interface{}) *gorm.DB
Delete(value interface{}, where ...interface{}) *gorm.DB
Find(out interface{}, where ...interface{}) *gorm.DB
DB() *sql.DB
Raw(sql string, values ...interface{}) *gorm.DB
Exec(sql string, values ...interface{}) *gorm.DB
Where(query interface{}, args ...interface{}) *gorm.DB
//other method signatures
}
type Handlers struct {
DB Store
}
func RegisterRoutes(router *gin.Engine, db Store) {
h := &Handlers{
DB: db,
}
routes := router.Group("/exercises")
routes.POST("/", h.AddExercise)
routes.GET("/", h.GetExercises)
routes.GET("/:id", h.GetExercise)
routes.PUT("/:id", h.UpdateExercise)
routes.DELETE("/:id", h.DeleteExercise)
}

Now, you can pass the *gorm.DB to the RegisterRoutes function in your code. For testing, you can use your MockDB struct if it implements all of the methods from the Store interface.