Testing without Bluetooth

Real radios are slow to test with: you need devices, and they must be near each other. package:dart_libp2p_ble/testing.dart gives in-memory radios that behave as BLE links do, so you can test your protocol, or a whole mesh, in flutter test.

import 'package:dart_libp2p_ble/testing.dart';

A network of radios

A FakeBleNetwork holds the radios. Every pair is in range unless you say otherwise, so you can build a partial mesh:

final network = FakeBleNetwork();
final radioA = network.newRadio();
final radioB = network.newRadio();
final radioC = network.newRadio();
network.setInRange(radioA, radioC, false); // A and C cannot hear each other

Give each radio to a BleTransport in place of BluetoothLowEnergyRadio. Everything above the radio is the real code: the transport, Noise, yamux, discovery and your protocols.

/// A node on [radio]: a host with only the BLE transport, gossipsub, and
/// discovery that connects to the nodes in range.
Future<(Host, PubSub, BleDiscovery)> _node(BleRadio radio) async {
  final keyPair = await generateEd25519KeyPair();
  final peerId = PeerId.fromPublicKey(keyPair.publicKey);
  final ble = BleTransport(radio: radio, localPeer: peerId);
  final host = await Libp2p.new_([
    Libp2p.identity(keyPair),
    Libp2p.transport(ble),
    Libp2p.listenAddrs([ble.listenAddr]),
    Libp2p.autoNAT(false),
    Libp2p.relay(false),
    Libp2p.autoRelay(false),
    Libp2p.holePunching(false),
  ]);
  await host.start();
  final pubsub = PubSub(host, GossipSubRouter());
  await pubsub.start();
  final discovery = BleDiscovery(host: host, transport: ble, yieldFor: const Duration(seconds: 1));
  return (host, pubsub, discovery);
}

A shorter yieldFor makes the test faster. On devices, keep the default.

The whole program is example/mesh_in_memory.dart: A sends a message on gossipsub, and C gets it through B.

flutter test test/examples_test.dart

What you can control

Setting	Default	What it does
FakeBleNetwork(maxValueLength:)	512	Largest GATT value. Set 20 or 182 to test small MTUs: connections split their writes into more values.
FakeBleNetwork(latency:)	none	Delay of each value. Values stay in order.
setInRange(a, b, false)	in range	a and b do not see each other and cannot connect. Links that are open stay open.
setRssi(a, b, dBm)	-50	The signal strength in the sightings a and b get of each other, for minRssi and swapMargin.
radio.openLinks		Number of links a radio has open, in both roles.

What it does not cover

The in-memory radios have no platform behavior: no permissions, no advertising limits, no changing peripheral IDs, and no lost links. Test on devices too before you ship; Platforms lists what is different on each.