fix config cli option (#7850)

cmd/platform/config_test.go

@@ -0,0 +1,29 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package main
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mattermost/mattermost-server/model"
+)
+
+func TestConfigValidate(t *testing.T) {
+	dir, err := ioutil.TempDir("", "")
+	require.NoError(t, err)
+	defer os.RemoveAll(dir)
+
+	path := filepath.Join(dir, "config.json")
+	config := &model.Config{}
+	config.SetDefaults()
+	require.NoError(t, ioutil.WriteFile(path, []byte(config.ToJson()), 0600))
+
+	assert.Contains(t, checkCommand(t, "--config", path, "config", "validate"), "The document is valid")
+}