Testing Websockets

While their utility is limited due to the nature of WebSockets, tests can be authored to verify websocket connections endpoints exist and are working as expected via the test.websockets.connect() method from @joystick.js/test:


import test from '@joystick.js/test';

test.that('the webscket message is sent and received on the server', async (assert = {}) => {
  const connection = await test.websockets.connect('chat_messages');

    message: 'Hey, did you get the Q3 report I sent?'


  const function_calls = await test.utils.get_function_calls('node.websockets.chat_messages.on_message'); 

  assert.like(function_calls[0]?.args[0], {
    message: 'Hey, did you get the Q3 report I sent?'

Above, using the test.websockets.connect() method, we establish a connection to a hypothetical chat_messages websocket endpoint. Next, we call the connection.send() method to send a payload containing a message we want to relay via WebSockets.

After our message is sent, we make sure to close the connection with connection.close() (important as open connections can cause the test runner to hang unexpectedly and time out).

Finally, to assert our message made it to the server, we call to test.utils.get_function_calls(), retrieving the value of node.websockets.chat_messages.on_message which is an array containing all calls to our chat_message WebSocket server's on_message() method.

To assert our test works, we check that the function calls to on_message() contains a message like the one we sent above.

API Reference


Function API

Function API

test.websockets.connect(server_name: string) => Promise;


  • server_name string Required

    The name of the WebSocket server to connect to.


  send: function,
  close: function,
  • send function

    A function receiving an object containing the message to send to the WebSocket server.

  • close function

    A function to close the open WebSocket connection.

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