add connections leak test

tests/conn_test.go

@@ -0,0 +1,24 @@
+package tests_test
+
+import (
+	"context"
+	"database/sql"
+	. "gorm.io/gorm/utils/tests"
+	"reflect"
+	"testing"
+)
+
+func TestConnLeak(t *testing.T) {
+
+	DB.Table("non_existent").WithContext(context.Background()).FirstOrCreate(&User{Name: "foo"})
+	DB.Table("non_existent").WithContext(context.Background()).FirstOrCreate(&User{Name: "foo"})
+	DB.Table("non_existent").WithContext(context.Background()).FirstOrCreate(&User{Name: "foo"})
+
+	connPool := DB.ConnPool.(*sql.DB)
+	v := reflect.ValueOf(connPool).Elem()
+	f := v.FieldByName("numOpen")
+
+	if f.Int() > 1 {
+		t.Errorf("Expected open one connections but found %d", f.Int())
+	}
+}