Mocking the method of a class returned from an exported function

Question

I'm wanting to mock a method of a class returned from a module's exports, and I'm having a hard time setting up a Jest test to do so.

Here's what I have:

// src/jwks.js

const jwksClient = require('jwks-rsa')
const client = jwksClient({...})
module.exports = client

// src/auth.js

const jwksClient = require('./jwks')

function getKey (header, callback) {
  jwksClient.getSigningKey(header.kid, function (err, key) {
    console.log("inside getSigningKey")
    var signingKey = key.publicKey || key.rsaPublicKey
    callback(err, signingKey)
  })
}

exports.getKey = getKey

// src/auth.test.js

const jwksClient = require('./jwks')
const { getKey } = require('./auth')

const mockGetSigningKey = jest.fn(() => {
    console.log("mockGetSigningKey called")
    return {
        publickey: "the-key"
    }
})

jest.mock('./jwks', () => {
  return jest.fn().mockImplementation(() => {
    return {
        getSigningKey: mockGetSigningKey
    }
  })
})

test('test mocked behavior', () => {
    getKey("somekey", (err, key) => {
        console.log("received key: " + key)
    })
}

I get the following error: TypeError: jwksClient.getSigningKey is not a function

  2 | 
  3 | function getKey (header, callback) {
> 4 |   jwksClient.getSigningKey(header.kid, function (err, key) {
    |              ^
  5 |     console.log("inside getSigningKey")
  6 |     var signingKey = key.publicKey || key.rsaPublicKey
  7 |     callback(err, signingKey)

How do I go about doing this properly? I've tried a lot of different variations and none of them are working for me.

Lin Du · Accepted Answer · 2020-06-24 02:49:42Z

You didn't mock ./jwks module correctly. Here is the solution:

auth.js:

const jwksClient = require('./jwks');

function getKey(header, callback) {
  jwksClient.getSigningKey(header.kid, function (err, key) {
    console.log('inside getSigningKey');
    var signingKey = key.publicKey || key.rsaPublicKey;
    callback(err, signingKey);
  });
}

exports.getKey = getKey;

jwks.js:

// whatever

auth.test.js:

const { getKey } = require('./auth');
const jwksClient = require('./jwks');

jest.mock('./jwks', () => {
  return { getSigningKey: jest.fn() };
});

describe('62544352', () => {
  it('should pass', () => {
    jwksClient.getSigningKey.mockImplementationOnce((key, callback) => {
      const key = { publicKey: 'publicKey' };
      callback(null, key);
    });
    const mCallback = jest.fn();
    getKey({ kid: 'someKey' }, mCallback);
    expect(jwksClient.getSigningKey).toBeCalledWith('someKey', expect.any(Function));
    expect(mCallback).toBeCalledWith(null, 'publicKey');
  });
});

unit test result with coverage report:

 PASS  stackoverflow/62544352/auth.test.js (10.232s)
  62544352
    ✓ should pass (28ms)

  console.log
    inside getSigningKey

      at stackoverflow/62544352/auth.js:5:13

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |     100 |       50 |     100 |     100 |                   
 auth.js  |     100 |       50 |     100 |     100 | 6                 
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        11.65s

Collectives™ on Stack Overflow

Mocking the method of a class returned from an exported function

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related