Decouple unit test code from business code (#17623)

modules/indexer/code/elastic_search_test.go

@@ -8,12 +8,13 @@ import (
 	"os"
 	"testing"
 
-	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
+
 	"github.com/stretchr/testify/assert"
 )
 
 func TestESIndexAndSearch(t *testing.T) {
-	db.PrepareTestEnv(t)
+	unittest.PrepareTestEnv(t)
 
 	u := os.Getenv("TEST_INDEXER_CODE_ES_URL")
 	if u == "" {