GODT-1917: gRPC service should use random port.

WIP: bridge-gui wait and parse gRPC service config fie.

internal/frontend/grpc/config_test.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package grpc
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+const (
+	dummyPort    = 12
+	dummyCert    = "A dummy cert"
+	dummyToken   = "A dummy token"
+	tempFileName = "test.json"
+)
+
+func TestConfig(t *testing.T) {
+	conf1 := config{
+		Port:  dummyPort,
+		Cert:  dummyCert,
+		Token: dummyToken,
+	}
+
+	// Read-back test
+	tempDir := t.TempDir()
+	tempFilePath := filepath.Join(tempDir, tempFileName)
+	require.NoError(t, conf1.save(tempFilePath))
+
+	conf2 := config{}
+	require.NoError(t, conf2.load(tempFilePath))
+	require.Equal(t, conf1, conf2)
+
+	// failure to load
+	require.Error(t, conf2.load(tempFilePath+"_"))
+
+	// failure to save
+	require.Error(t, conf2.save(filepath.Join(tempDir, "non/existing/folder", tempFileName)))
+}