You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: expirynotify_test.go
    path of file: ./repos/mattermost/server/channels/app
    
    the code of the file until where you have to start completion: // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

package app

import (
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/stretchr/testify/require"

	"github.com/mattermost/matt
    
func TestNotifySessionsExpired(t *testing.T) {
	th := Setup(t).InitBasic()
	defer th.TearDown()

	handler := &testPushNotificationHandler{t: t}
	pushServer := httptest.NewServer(
		http.HandlerFunc(handler.handleReq),
	)
	defer pushServer.Close()

	th.App.UpdateConfig(func(cfg *model.Config) {
		*cfg.EmailSettings.PushNotificationServer = pushServer.URL
	})

	t.Run("push notifications disabled", func(t *testing.T) {
		th.App.UpdateConfig(func(cfg *model.Config) {
			*cfg.EmailSettings.SendPushNotifications = false
		})

		err := th.App.NotifySessionsExpired()
		// no error, but also no requests sent
		require.NoError(t, err)
		require.Equal(t, 0, handler.numReqs())
	})

	t.Run("two sessions expired", func(t *testing.T) {
		th.App.UpdateConfig(func(cfg *model.Config) {
			*cfg.EmailSettings.SendPushNotifications = true
		})

		data := []struct {
			deviceID  string
			expiresAt int64
			notified  bool
		}{
			{deviceID: "android:11111", expiresAt: model.GetMillis() + 100000, notified: false},
			{deviceID: "android:22222", expiresAt: model.GetMillis() - 1000, notified: false},
			{deviceID: "android:33333", expiresAt: model.GetMillis() - 2000, notified: false},
			{deviceID: "android:44444", expiresAt: model.GetMillis() - 3000, notified: true},
		}

		for _, d := range data {
			_, err := th.App.CreateSession(th.Context, &model.Session{
				UserId:        th.BasicUser.Id,
				DeviceId:      d.deviceID,
				ExpiresAt:     d.expiresAt,
				ExpiredNotify: d.notified,
			})
			require.Nil(t, err)
		}

		err := th.App.NotifySessionsExpired()
		require.NoError(t, err)
		require.Equal(t, 2, handler.numReqs())

		expected := []string{"22222", "33333"}
		require.Equal(t, model.PushTypeSession, handler.notifications()[0].Type)
		require.Contains(t, expected, handler.notifications()[0].DeviceId)
		require.Contains(t, handler.notifications()[0].Message, "Session Expired")

		require.Equal(t, model.PushTypeSession, handler.notifications()[1].Type)
		require.Contains(t, expected, handler.notifications()[1].DeviceId)
		require.Contains(t, handler.notifications()[1].Message, "Session Expired")
	})
}