@relaycorp/ws-mock

@relaycorp/ws-mock

Mock client and server to unit test the NPM package ws.

Install

npm install @relaycorp/ws-mock

Using the mock client

You should initialise MockClient by passing the ws server to be tested and then call client.connect() to initiate the connection. From that point you can interact with the server. For example:

  test('Challenge should be sent as soon as client connects', async () => {
    const client = new MockClient(wsServer);
    await client.connect();

    const challengeSerialized = await client.receive();
    expect(challengeSerialized).toBeInstanceOf(ArrayBuffer);
  });

You'll find real-world examples in relaycorp/relaynet-internet-gateway.

Using the mock server

Simply initialise MockServer with the ws client connection you wish to test. For example:

  test('Server message should be played back', async () => {
    const mockConnection = new MockConnection();
    const mockServer = new MockServer(mockConnection);
    const clientUnderTest = new ClientUnderTest(mockConnection);

    clientUnderTest.connectToServer();
    mockServer.send('foo');

    const clientResponse = await mockServer.receive();
    expect(clientResponse).toEqual('foo');
  });

You'll find real-world examples in relaycorp/relaynet-poweb-js.

Using streams

When using streams in the unit under test, make sure to mock the createWebSocketStream function in ws. Here's an example with Jest:

import { createMockWebSocketStream } from '@relaycorp/ws-mock';
import WebSocket from 'ws';

jest.spyOn(WebSocket, 'createWebSocketStream').mockImplementation(createMockWebSocketStream);