Add migrations tests (#34456) (#34483)

Backport #34456 by @lunny

Fix #34455

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/migrations/v1_23/v304_test.go

@@ -0,0 +1,40 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_23 //nolint
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/base"
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_AddIndexForReleaseSha1(t *testing.T) {
+	type Release struct {
+		ID               int64  `xorm:"pk autoincr"`
+		RepoID           int64  `xorm:"INDEX UNIQUE(n)"`
+		PublisherID      int64  `xorm:"INDEX"`
+		TagName          string `xorm:"INDEX UNIQUE(n)"`
+		OriginalAuthor   string
+		OriginalAuthorID int64 `xorm:"index"`
+		LowerTagName     string
+		Target           string
+		Title            string
+		Sha1             string `xorm:"VARCHAR(64)"`
+		NumCommits       int64
+		Note             string             `xorm:"TEXT"`
+		IsDraft          bool               `xorm:"NOT NULL DEFAULT false"`
+		IsPrerelease     bool               `xorm:"NOT NULL DEFAULT false"`
+		IsTag            bool               `xorm:"NOT NULL DEFAULT false"` // will be true only if the record is a tag and has no related releases
+		CreatedUnix      timeutil.TimeStamp `xorm:"INDEX"`
+	}
+
+	// Prepare and load the testing database
+	x, deferable := base.PrepareTestEnv(t, 0, new(Release))
+	defer deferable()
+
+	assert.NoError(t, AddIndexForReleaseSha1(x))
+}