Create part of XX test and update code accordingly

test/xx.test.ts

@@ -1,5 +1,7 @@
-import { expect } from "chai";
+import { expect, assert } from "chai";
 import { Buffer } from 'buffer';
+import * as crypto from 'libp2p-crypto';
+import protobuf from 'protobufjs';
 
 import { XXHandshake, KeyPair } from "../src/xx";
 
@@ -28,4 +30,50 @@ describe("Index", () => {
     expect(k2.toString('hex')).to.equal('a16ada915e551ab623f38be674bb4ef15d428ae9d80688899c9ef9b62ef208fa');
     expect(k3.toString('hex')).to.equal('ff67bf9727e31b06efc203907e6786667d2c7a74ac412b4d31a80ba3fd766f68');
   })
+
+  async function generateKeypair() {
+    return await crypto.keys.generateKeyPair('ed25519');;
+  }
+
+  async function doHandshake() {
+    const xx = new XXHandshake();
+    const kpInit = await xx.generateKeypair();
+    const kpResp = await xx.generateKeypair();
+    const payloadString = Buffer.from("noise-libp2p-static-key:");
+
+    // initiator setup
+    const libp2pInitKeys = await generateKeypair();
+    const initSignedPayload = await libp2pInitKeys.sign(Buffer.concat([payloadString, kpInit.publicKey]));
+
+    // responder setup
+    const libp2pRespKeys = await generateKeypair();
+    const respSignedPayload = await libp2pRespKeys.sign(Buffer.concat([payloadString, kpResp.publicKey]));
+
+    // initiator: new XX noise session
+    const nsInit = await xx.initSession(true, prologue, kpInit, kpResp.publicKey);
+    // responder: new XX noise session
+    const nsResp = await xx.initSession(false, prologue, kpResp, kpInit.publicKey);
+
+    /* stage 0: initiator */
+
+    // initiator creates payload
+    const payloadProtoBuf = await protobuf.load("payload.proto");
+    const NoiseHandshakePayload = payloadProtoBuf.lookupType("pb.NoiseHandshakePayload");
+    const payloadInit = NoiseHandshakePayload.create({
+      libp2pKey: libp2pInitKeys.bytes.toString('hex'),
+      noiseStaticKeySignature: initSignedPayload,
+    });
+
+    const payloadInitEnc = NoiseHandshakePayload.encode(payloadInit).finish();
+
+    // initiator sends message
+    const message = Buffer.concat([Buffer.alloc(0), payloadInitEnc]);
+    const messageBuffer = await xx.sendMessage(nsInit, message);
+
+    expect(messageBuffer.ne.length).not.equal(0);
+  }
+
+  it("Test handshake", async () => {
+    await doHandshake();
+  })
 });