func TestUpdate(t *testing.T) {
	results := []struct {
		Clauses []clause.Interface
		Result  string
		Vars    []interface{}
	}{
		{
			[]clause.Interface{clause.Update{}},
			"UPDATE `users`", nil,
		},
		{
			[]clause.Interface{clause.Update{Modifier: "LOW_PRIORITY"}},
			"UPDATE LOW_PRIORITY `users`", nil,
		},
		{
			[]clause.Interface{clause.Update{Table: clause.Table{Name: "products"}, Modifier: "LOW_PRIORITY"}},

	}

	if err := DB.Model(&results[0]).Updates(map[string]interface{}{"age": gorm.Expr("age + ?", 100)}).Error; err != nil {
		t.Errorf("Not error should happen when updating with gorm expr, but got %v", err)
	}

	if err := DB.Model(&results[1]).Clauses(clause.Returning{Columns: []clause.Column{{Name: "age"}}}).Updates(map[string]interface{}{"age": gorm.Expr("age + ?", 100)}).Error; err != nil {