controlplane: xds unit tests (#770)

* xds: use plain functions, add unit tests for control plane routes

* xds: add test for grpc routes

* xds: add test for pomerium http routes

* xds: add test for policy routes

* xds: use plain functions

* xds: test get all routeable domains

* xds: add build downstream tls context test

* more tests

* test for client cert

* more tests

internal/testutil/testutil.go

@@ -0,0 +1,34 @@
+// Package testutil contains helper functions for unit tests.
+package testutil
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/golang/protobuf/proto"
+	"github.com/stretchr/testify/assert"
+	"google.golang.org/protobuf/encoding/protojson"
+)
+
+// AssertProtoJSONEqual asserts that a protobuf message matches the given JSON. The protoMsg can also be a slice
+// of protobuf messages.
+func AssertProtoJSONEqual(t *testing.T, expected string, protoMsg interface{}, msgAndArgs ...interface{}) bool {
+	protoMsgVal := reflect.ValueOf(protoMsg)
+	if protoMsgVal.Kind() == reflect.Slice {
+		var protoMsgs []json.RawMessage
+		for i := 0; i < protoMsgVal.Len(); i++ {
+			protoMsgs = append(protoMsgs, toProtoJSON(protoMsgVal.Index(i).Interface()))
+		}
+		bs, _ := json.Marshal(protoMsgs)
+		return assert.JSONEq(t, expected, string(bs), msgAndArgs...)
+	}
+
+	return assert.JSONEq(t, expected, string(toProtoJSON(protoMsg)), msgAndArgs...)
+}
+
+func toProtoJSON(protoMsg interface{}) json.RawMessage {
+	v2 := proto.MessageV2(protoMsg)
+	bs, _ := protojson.Marshal(v2)
+	return bs
+}