save function throwing error in one case and not throwing error in another case

mockTestDB_return_configurable.go

type mockTestDB1 struct {}
type mockTestDB2 struct {}

func (m *mockTestDB1) Save(person *Person) error {
	// case 1
	return nil
}

func (m *mockTestDB2) Save(person *Person) error {
	// case 2 
	return fmt.Errorf("error in save")
}