CODEWITHSUNDEEP
node.jstestingjestjs
rafaelpolonio
rafaelpolonio

Reputation: 47

Stubbing function with jest to test Internal error

I'm trying to test a controller function using jest, and i want to test all three status return

const messagesSender = async (req, res) => {
  try {
    const { message } = req.body;
    if (!message) {
      return res.status(400).send({ message: 'Message cannot be null' });
    }
    return res.status(200).send(message);
  } catch (error) {
    return res.status(500).json({ error: 'Internal Error' });
  }
};

module.exports = { messagesSender };

Test file:

const messages = require('../controller/messagesController');

describe('Testing Messages Controller', () => {

  it('should return internal error', async () => {
    const req = {
      body: {
        message: 'testing',
      },
    };
    const res = {
      send: jest.fn(),
      status: jest.fn(() => res),
    };
    const messageResponse = await messages.messagesSender(req, res);
    messageResponse.mockImplementation(() => {
      throw new Error('User not found');
    });
    expect(res.status).toBeCalledWith(500);
  });
});

But i'm receiving the error:

TypeError: Cannot read property 'mockImplementation' of undefined

How can i fix this and test the 500 result?

Upvotes: 0

Views: 386

Answers (1)

Andrey Nelubin
Andrey Nelubin

Reputation: 3294

  it('should return internal error', async () => {
    const req = {
      body: {
        message: 'testing',
      },
    };
    const res = {
      send: jest.fn().mockImplementation(() => {
        throw new Error('User not found');
      }),
      status: jest.fn(() => res),
    };
    await messages.messagesSender(req, res);
    expect(res.status.mock.calls[1][0]).toBe(500);
  });

In your case send function returning nothing and causing this problem. In this case status method have been called twice, so you need to check the second call.

Upvotes: 1

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