Unit testing with gorm - unit-testing

Question

I have found a lot of questions regarding gorm mocking related to the old V1 package: github.com/jinzhu/gorm. with the usage of github.com/DATA-DOG/go-sqlmock.
I didn't find much with the v2.
My simple question is:
Suppose I have this storage package code:
...
type Storage struct {
GormDB *gorm.DB
SqlDB *sql.DB
mutex sync.Mutex
ReadTimeout int
WriteTimeout int
}
func (ps *Storage) Open(settings *Settings) error {
if err := settings.Validate(); err != nil {
return err
}
ps.mutex.Lock()
defer ps.mutex.Unlock()
if ps.GormDB != nil {
return nil
}
gormDB, err := gorm.Open(postgres.New(postgres.Config{
DSN: settings.GetDSN(),
}), &gorm.Config{
SkipDefaultTransaction: true,
})
if err != nil {
return fmt.Errorf("%s: %v", DBConnectError, err)
}
ps.GormDB = gormDB
sqlDB, err := ps.GormDB.DB()
if err != nil {
return fmt.Errorf("%s: %v", DBRetrievalError, err)
}
ps.SqlDB = sqlDB
ps.SqlDB.SetMaxIdleConns(settings.MaxIdleConnections)
ps.SqlDB.SetMaxOpenConns(settings.MaxOpenConnections)
ps.ReadTimeout = settings.ReadTimeout
ps.WriteTimeout = settings.WriteTimeout
return nil
}
How can I unit-test this function with a simple check that gorm.Open received the expected config?
I don't see any other way than passing the ORM interface to this method... It would be a tough solution to write a gorm interface and mock it myself...
Can anyone please provide a simple example of mocking such a function?
P.S.
I don't want to run the docker with Postgres for this test. It is a simple unit test, not integration.
EDIT:
Suppose I just want to mock the connection to make gorm.Open to not return an error. How can I do it?
sqlmock.NewWithDSN(settings.GetDSN()) does not help

Answer 1

Answering my own question here.
Thanks to #flimzy for pointing me in the right direction.
To be able to test the storage open need to modify the function:
func (ps *Storage) Open(settings *Settings, postgresConfig *postgres.Config) error {
if err := settings.Validate(); err != nil {
return err
}
ps.mutex.Lock()
defer ps.mutex.Unlock()
if ps.GormDB != nil {
return nil
}
gormDB, err := gorm.Open(postgres.New(*postgresConfig), &gorm.Config{
SkipDefaultTransaction: true,
})
if err != nil {
return fmt.Errorf("%s: %v", DBConnectError, err)
}
ps.GormDB = gormDB
sqlDB, err := ps.GormDB.DB()
if err != nil {
return fmt.Errorf("%s: %v", DBRetrievalError, err)
}
ps.SqlDB = sqlDB
ps.SqlDB.SetMaxIdleConns(settings.MaxIdleConnections)
ps.SqlDB.SetMaxOpenConns(settings.MaxOpenConnections)
ps.ReadTimeout = settings.ReadTimeout
ps.WriteTimeout = settings.WriteTimeout
return nil
}
To mock gorm connection we just pass go-sqlmock connection in the postgres config of the form postgres driver:
package postgres
import (
"github.com/DATA-DOG/go-sqlmock"
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
)
var _ = Describe("Postgres Storage", func() {
...
Describe("Open", func() {
Context("when settings are valid", func() {
It("should open a DB connection and initialize storage", func() {
sqlDB, sqlMock, _ := sqlmock.New()
sqlMock.ExpectPing()
err := storage.Open(settings, postgres.Config{Conn: sqlDB})
dbStats := storage.sqlDB.Stats()
Expect(err).ShouldNot(HaveOccurred())
Expect(dbStats.MaxOpenConnections).To(Equal(settings.MaxOpenConnections))
Expect(dbStats.OpenConnections).To(Equal(1))
Expect(storage.ReadTimeout).To(Equal(settings.ReadTimeout))
Expect(storage.WriteTimeout).To(Equal(settings.WriteTimeout))
Expect(sqlMock.ExpectationsWereMet()).To(BeNil())
})
})
})
})