test: reproduce empty payload issue

lib/src/cln_grpc_base.dart

@@ -97,6 +97,7 @@ class GRPCClient extends LightningClient {
       {required ListfundsRequest params, T Function(Map)? onDecode}) async {
     /// request to server
     var response = await stub.listFunds(params);
+    LogManager.getInstance.debug("response received by GRPC server: $response");
     if (onDecode != null) {
       return onDecode(toEncode(response.toProto3Json()));
     }

test/cln_client_test.dart

@@ -156,7 +156,7 @@ void main() {
       };
       var boltString = await unixCient.simpleCall("invoice", params: params);
       try {
-        var response = await client.call<PayProxy, PayResponse>(
+        var _ = await client.call<PayProxy, PayResponse>(
             method: "pay",
             params: PayProxy.build(invoice: boltString["bolt11"]));
         await client.close();

test/cln_grpc_test.dart

@@ -1,8 +1,11 @@
 import 'dart:io';
 
+import 'package:cln_common/cln_common.dart';
 import 'package:cln_grpc/cln_grpc.dart';
 import 'package:test/test.dart';
 
+import 'model/model.dart';
+
 void main() {
   var env = Platform.environment;
   var tlsPath = env['TLS_PATH']!;
@@ -14,5 +17,33 @@ void main() {
       expect(response.alias, "clighting4j-node");
       await client.close();
     });
+
+    test('Generic List Funds with decode function', () async {
+      var client = GRPCClient(rootPath: tlsPath);
+      var response =
+          await client.call<CLNListFundsRequest, Map<String, dynamic>>(
+              method: "listfunds",
+              params: CLNListFundsRequest.build(),
+              onDecode: (jsonResponse) {
+                LogManager.getInstance
+                    .debug("Grpc list funds call returns: $jsonResponse");
+                return jsonResponse as Map<String, dynamic>;
+              });
+      expect(response.isNotEmpty, isTrue);
+    });
+
+    test('Stub List Funds with decode function', () async {
+      var client = GRPCClient(rootPath: tlsPath);
+      var response = await client.listFunds(
+          params: CLNListFundsRequest.build().proxy, onDecode: (json) => json);
+      expect(response.isNotEmpty, isTrue);
+    });
+
+    test('Stub List Funds without decode function', () async {
+      var client = GRPCClient(rootPath: tlsPath);
+      var response = await client.listFunds<ListfundsResponse>(
+          params: CLNListFundsRequest.build().proxy);
+      expect(response.channels.isEmpty, isTrue);
+    });
   });
 }

test/model/model.dart

@@ -0,0 +1,17 @@
+import 'package:cln_common/cln_common.dart';
+import 'package:cln_grpc/cln_grpc.dart';
+
+class CLNListFundsRequest extends Serializable {
+  ListfundsRequest proxy;
+
+  CLNListFundsRequest(this.proxy);
+
+  factory CLNListFundsRequest.build() =>
+      CLNListFundsRequest(ListfundsRequest());
+
+  @override
+  Map<String, dynamic> toJSON() => proxy.toProto3Json() as Map<String, dynamic>;
+
+  @override
+  T as<T>() => proxy as T;
+}