How to test Discord bot commands with Jest?

Other Questions Discord bot
1

I’m working on a Discord bot and want to use Jest for testing. My bot file has an execute function that sends messages using discord.js. How can I test this without actually sending messages?

Here’s what I’m trying to do:

  1. Check if message.channel.send was called with the right text
  2. Mock the function so it doesn’t really send anything

I can run the command, but I’m not sure how to check what’s inside message.channel.send. I can’t make a real message object, so that might need mocking too.

Also, how should I test commands that return values?

// Example of what I'm working with
module.exports = {
  name: 'ping',
  execute(client, message) {
    message.channel.send('Pong!');
  }
};

Any tips on setting up Jest tests for this kind of Discord bot code would be super helpful!

2

As someone who’s been through the trenches of Discord bot testing, I can share some insights that might help you out.

For testing your execute function without sending real messages, mocking is your best friend. You’ll want to mock the entire discord.js library, including the Message object and its channel.send method. In my approach, I set up a discord.js mock in my test file and create a fake Message object that includes a mocked channel.send function. I then call my execute function with these mocks and use Jest’s expect().toHaveBeenCalledWith() to verify that the expected text was passed to channel.send. When testing commands that return values, I assert directly on the return value. I always make sure to reset my mocks between tests so they don’t interfere with one another. This setup requires a bit of configuration, but it reliably allows you to test your bot commands without ever hitting the live Discord API.

3

hey mate, i’ve been there too. mocking’s the way for sure. jest.mock(‘discord.js’) works wonders. create a fake message with a mocked channel.send, call execute, and then expect it to be called with ‘Pong!’. for returns, just assert the value. hope it helps!

4

Having worked on Discord bots myself, I can offer some practical advice for testing with Jest. The key is to mock the discord.js library and its components. Create a mock for the Message object and its channel.send method. Then, in your test, call the execute function with these mocks.

You can use Jest’s spyOn to monitor the channel.send calls and assert that it was called with the correct arguments. For commands that return values, simply call the function and assert on the return value directly.

Here’s a basic example:

jest.mock('discord.js');
const command = require('./yourCommandFile');

test('ping command sends correct message', () => {
  const mockSend = jest.fn();
  const mockMessage = { channel: { send: mockSend } };
  
  command.execute(null, mockMessage);
  
  expect(mockSend).toHaveBeenCalledWith('Pong!');
});

This approach allows you to test your bot’s logic without sending real messages or connecting to Discord’s API.