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: config_test.go
    path of file: ./repos/mattermost/server/channels/app/platform
    
    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 platform

import (
	"errors"
	"sync"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/mock"
	"github.com/stretchr/testify/require"

	"github.com/mattermost/mattermost/server/public/model"
	smocks "github.com/mattermost/mattermost/server/v8/channels/store/storetest/mocks"
	"github.com/mattermost/mattermost/server/v8/einterfaces/mocks"
)

func TestConfigListener(t *testing.T) {
	th := Setup(t)
	defer th.TearDown()

	originalSiteName := th.Service.Config().TeamSettings.SiteName

	listenerCalled := false
	listener := func(oldConfig *model.Config, newConfig *model.Config) {
		assert.False(t, listenerCalled, "listener called twice")

		assert.Equal(t, *originalSiteName, *oldConfig.TeamSettings.SiteName, "old config contains incorrect site name")
		assert.Equal(t, "test123", *newConfig.TeamSettings.SiteName, "new config contains incorrect site name")

		listenerCalled = true
	}
	listenerId := th.Service.AddConfigListener(listener)
	defer th.Service.RemoveConfigListener(listenerId)

	listener2Called := false
	listener2 := func(oldConfig *model.Config, newConfig *model.Config) {
		assert.False(t, listener2Called, "listener2 called twice")

		listener2Called = true
	}
	listener2Id := th.Service.AddConfigListener(listener2)
	defer th.Service.RemoveConfigListener(listener2Id)

	th.Service.UpdateConfig(func(cfg *model.Config) {
		*cfg.TeamSettings.SiteName = "test123"
	})

	assert.True(t, listenerCalled, "listener should've been called")
	assert.True(t, listener2Called, "listener 2 should've been called")
}

func TestConfigSave(t *testing.T) {
	cm := &mocks.ClusterInterface{}
	cm.On("SendClusterMessage", mock.AnythingOfType("*model.ClusterMessage")).Return(nil)
	th := SetupWithCluster(t, cm)
	defer th.TearDown()

	
    
func TestConfigSave(t *testing.T) {
	cm := &mocks.ClusterInterface{}
	cm.On("SendClusterMessage", mock.AnythingOfType("*model.ClusterMessage")).Return(nil)
	th := SetupWithCluster(t, cm)
	defer th.TearDown()

	t.Run("trigger a config changed event for the cluster", func(t *testing.T) {
		oldCfg := th.Service.Config()
		newCfg := oldCfg.Clone()
		newCfg.ServiceSettings.SiteURL = model.NewString("http://newhost.me")

		sanitizedOldCfg := th.Service.configStore.RemoveEnvironmentOverrides(oldCfg)
		sanitizedNewCfg := th.Service.configStore.RemoveEnvironmentOverrides(newCfg)
		cm.On("ConfigChanged", sanitizedOldCfg, sanitizedNewCfg, true).Return(nil)

		_, _, appErr := th.Service.SaveConfig(newCfg, true)
		require.Nil(t, appErr)

		updatedCfg := th.Service.Config()
		assert.Equal(t, "http://newhost.me", *updatedCfg.ServiceSettings.SiteURL)
	})

	t.Run("do not restart the metrics server on a different type of config change", func(t *testing.T) {
		th := Setup(t, StartMetrics())
		defer th.TearDown()

		metricsMock := &mocks.MetricsInterface{}
		metricsMock.On("IncrementWebsocketEvent", model.WebsocketEventConfigChanged).Return()
		metricsMock.On("IncrementWebSocketBroadcastBufferSize", mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
		metricsMock.On("DecrementWebSocketBroadcastBufferSize", mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
		metricsMock.On("Register").Return()
		th.Service.metricsIFace = metricsMock

		// Change a random config setting
		cfg := th.Service.Config().Clone()
		cfg.ThemeSettings.EnableThemeSelection = model.NewBool(!*cfg.ThemeSettings.EnableThemeSelection)
		th.Service.SaveConfig(cfg, false)
		metricsMock.AssertNumberOfCalls(t, "Register", 0)

		// Disable metrics
		cfg.MetricsSettings.Enable = model.NewBool(false)
		th.Service.SaveConfig(cfg, false)

		// Change the metrics setting
		cfg.MetricsSettings.Enable = model.NewBool(true)
		th.Service.SaveConfig(cfg, false)
		metricsMock.AssertNumberOfCalls(t, "Register", 1)
	})
}