feat: accept preconfigured PeerConnection as polyfill arg

src/polyfill/RTCPeerConnection.ts

@@ -12,6 +12,7 @@ import RTCCertificate from './RTCCertificate';
 // extend RTCConfiguration with peerIdentity
 interface RTCConfiguration extends globalThis.RTCConfiguration {
     peerIdentity?: string;
+    peerConnection?: PeerConnection;
 }
 
 export default class RTCPeerConnection extends EventTarget implements globalThis.RTCPeerConnection {
@@ -121,7 +122,7 @@ export default class RTCPeerConnection extends EventTarget implements globalThis
 
         try {
             const peerIdentity = (config as any)?.peerIdentity ?? `peer-${getRandomString(7)}`;
-            this.#peerConnection = new PeerConnection(peerIdentity,
+            this.#peerConnection = config.peerConnection ?? new PeerConnection(peerIdentity,
                 {
                     ...config,
                     iceServers:

test/jest-tests/polyfill.test.ts

@@ -1,5 +1,6 @@
-import { expect } from '@jest/globals';
+import { expect, jest } from '@jest/globals';
 import { RTCPeerConnection, RTCDataChannel } from '../../src/polyfill/index';
+import { PeerConnection } from '../../src/lib/index';
 
 describe('polyfill', () => {
     // Default is 5000 ms but we need more
@@ -212,4 +213,26 @@ describe('polyfill', () => {
 			};
 		});
 	});
+
+	test('it should accept a preconfigured PeerConnection', () => {
+		const peerConnection = new PeerConnection('Peer', {
+				iceServers: [],
+		});
+
+		// have to override write-only method in order to spy on it
+		const originalFunc = peerConnection.state.bind(peerConnection);
+		Object.defineProperty(peerConnection, 'state', {
+				value: originalFunc,
+				writable: true,
+				enumerable: true,
+		});
+
+		const spy = jest.spyOn(peerConnection, 'state');
+		const rtcPeerConnection = new RTCPeerConnection({
+				peerConnection,
+		});
+		const connectionState = rtcPeerConnection.connectionState;
+		expect(spy).toHaveBeenCalled();
+		expect(connectionState).toEqual(originalFunc());
+});
 });