services/filestore: migrate s3store_test to testify (#12685)

* services/filestore: migrate s3store_test to testify

* services/filestore: s3_store_test.go polished

services/filesstore/s3store_test.go

@@ -7,26 +7,23 @@ import (
 	"testing"
 
 	"github.com/mattermost/mattermost-server/model"
+	"github.com/stretchr/testify/require"
 )
 
 func TestCheckMandatoryS3Fields(t *testing.T) {
 	cfg := model.FileSettings{}
 
 	err := CheckMandatoryS3Fields(&cfg)
-	if err == nil || err.Message != "api.admin.test_s3.missing_s3_bucket" {
-		t.Fatal("should've failed with missing s3 bucket")
-	}
+	require.NotNil(t, err)
+	require.Equal(t, err.Message, "api.admin.test_s3.missing_s3_bucket", "should've failed with missing s3 bucket")
 
 	cfg.AmazonS3Bucket = model.NewString("test-mm")
 	err = CheckMandatoryS3Fields(&cfg)
-	if err != nil {
-		t.Fatal("should've not failed")
-	}
+	require.Nil(t, err)
 
 	cfg.AmazonS3Endpoint = model.NewString("")
 	err = CheckMandatoryS3Fields(&cfg)
-	if err != nil || *cfg.AmazonS3Endpoint != "s3.amazonaws.com" {
-		t.Fatal("should've not failed because it should set the endpoint to the default")
-	}
 
+	require.Nil(t, err)
+	require.Equal(t, *cfg.AmazonS3Endpoint, "s3.amazonaws.com", "should've set the endpoint to the default")
 }