Typescript Node test cannot redifine property?

Question

So i have this test doing in my typescript project and when i do the mock tests two test have been failing all the issues are related to TypeError [Error]: Cannot redefine property: fetchAndNormalizePullRequests i looked all the way and couldn't find a way to fix the issue. this is the

pull-request.handler.test.ts

import { test, describe, beforeEach, afterEach, mock } from 'node:test';
import assert from 'node:assert';
import type { Request, Response } from 'express';
import { getAllPullRequests } from '../../handlers/pull-requests.handler.js';

const originalEnv = process.env;
// const pullRequestsService = await import('../../services/pull-requests.service.js');

describe('Pull Requests Handler', () => {
  let mockReq: Partial<Request>;
  let mockRes: Partial<Response>;
  let statusMock: any;
  let jsonMock: any;
  let fetchMock: any;

  beforeEach(() => {
    mock.restoreAll();

    statusMock = mock.fn(() => mockRes);
    jsonMock = mock.fn();
    
    mockRes = {
      status: statusMock,
      json: jsonMock
    };

    process.env = { ...originalEnv };
  });

  afterEach(() => {
    process.env = originalEnv;
    mock.restoreAll();
  });

  test('should return 500 when GITHUB_API_TOKEN is missing', async () => {
    delete process.env.GITHUB_API_TOKEN;
    mockReq = {
      query: { owner: 'testowner', repo: 'testrepo' }
    };

    await getAllPullRequests(mockReq as Request, mockRes as Response);

    assert.strictEqual(statusMock.mock.callCount(), 1);
    assert.deepStrictEqual(statusMock.mock.calls[0].arguments, [500]);
    assert.strictEqual(jsonMock.mock.callCount(), 1);
    assert.deepStrictEqual(jsonMock.mock.calls[0].arguments, [{ error: 'Missing environment variables.' }]);
  });

  test('should return 500 when owner is missing', async () => {
    process.env.GITHUB_API_TOKEN = 'test-token';
    mockReq = {
      query: { repo: 'testrepo' }
    };

    try{
    await getAllPullRequests(mockReq as Request, mockRes as Response);
    }
    catch(e){
      console.error(e);
    }

    assert.strictEqual(statusMock.mock.callCount(), 1);
    assert.deepStrictEqual(statusMock.mock.calls[0].arguments, [500]);
    assert.strictEqual(jsonMock.mock.callCount(), 1);
    assert.deepStrictEqual(jsonMock.mock.calls[0].arguments, [{ error: 'Missing environment variables.' }]);
  });

  test('should return 500 when repo is missing', async () => {
    process.env.GITHUB_API_TOKEN = 'test-token';
    mockReq = {
      query: { owner: 'testowner' }
    };

    await getAllPullRequests(mockReq as Request, mockRes as Response);

    assert.strictEqual(statusMock.mock.callCount(), 1);
    assert.deepStrictEqual(statusMock.mock.calls[0].arguments, [500]);
    assert.strictEqual(jsonMock.mock.callCount(), 1);
    assert.deepStrictEqual(jsonMock.mock.calls[0].arguments, [{ error: 'Missing environment variables.' }]);
  });

  test('should return 200 with pull requests when all parameters are valid', async () => {
    process.env.GITHUB_API_TOKEN = 'test-token';
    mockReq = {
      query: { owner: 'testowner', repo: 'testrepo' }
    };

    const mockPullRequests = [
      {
        prNumber: 1,
        title: 'Test PR',
        creator: 'testuser',
        creationTimestamp: '2024-01-01T00:00:00Z',
        requestedReviewers: ['reviewer1'],
        lastActionType: 'open',
        lastActionTimestamp: '2024-01-01T00:00:00Z'
      }
    ];

    const fetchMock = mock.fn(() => Promise.resolve(mockPullRequests));
    mock.method(await import('../../services/pull-requests.service.js'), 'fetchAndNormalizePullRequests', fetchMock);

    await getAllPullRequests(mockReq as Request, mockRes as Response);

    assert.strictEqual(statusMock.mock.callCount(), 1);
    assert.deepStrictEqual(statusMock.mock.calls[0].arguments, [200]);
    assert.strictEqual(jsonMock.mock.callCount(), 1);
    assert.deepStrictEqual(jsonMock.mock.calls[0].arguments, [mockPullRequests]);
  });

  test('should return 500 when service throws an error', async () => {
    process.env.GITHUB_API_TOKEN = 'test-token';
    mockReq = {
      query: { owner: 'testowner', repo: 'testrepo' }
    };

    const fetchMock = mock.fn(() => Promise.reject(new Error('Service error')));
    mock.method(await import('../../services/pull-requests.service.js'), 'fetchAndNormalizePullRequests', fetchMock);

    await getAllPullRequests(mockReq as Request, mockRes as Response);

    assert.strictEqual(statusMock.mock.callCount(), 1);
    assert.deepStrictEqual(statusMock.mock.calls[0].arguments, [500]);
    assert.strictEqual(jsonMock.mock.callCount(), 1);
    assert.deepStrictEqual(jsonMock.mock.calls[0].arguments, [{ error: 'Internal server error.' }]);
  });
});

and this is my fetchAndNormalizePullRequest function

import axios from 'axios';
import type{ NormalizedPR } from '../types/types.js';

export const fetchAndNormalizePullRequests = async (owner: string, repo: string, token: string): Promise<NormalizedPR[]> => {
  const url = `https://api.github.com/repos/${owner}/${repo}/pulls?state=all`;

  try {
    const response = await axios.get(url, {
      headers: {
        Authorization: `token ${token}`,
        'Content-Type': 'application/json',
      },
    });

    return response.data.map((pr: any) => ({
      prNumber: pr.number,
      title: pr.title,
      creator: pr.user.login,
      creationTimestamp: pr.created_at,
      requestedReviewers: pr.requested_reviewers.map((reviewer: any) => reviewer.login),
      lastActionType: pr.merged_at ? 'merged' : pr.state,
      lastActionTimestamp: pr.updated_at,
    }));
  } catch (error) {
    throw new Error('Failed to fetch pull requests from GitHub API.');
  }
};

what am i doing wrong? can't fix the issue

fetchAndNormalizePullRequests is a named ESM export from pull-requests.service.js. The thing you get from await import('../../services/pull-requests.service.js') is a module namespace object. Module namespace properties that correspond to named exports are immutable and non-configurable. — mplungjan
– mplungjan, Commented Sep 22 at 15:32

MoshMage · Accepted Answer · 2025-09-23 10:53:35Z

When you

mock.method(await import('../../services/pull-requests.service.js'), 'fetchAndNormalizePullRequests', fetchMock);

You're trying to mock a method, but your pull-requests.service.js is a module, so in essence you're trying to change a ESM module instead of the method.

To achieve what you want, you should do something like:


/** placeholder variables to be assigned later */
let getAllPullRequests;
let mockedFetchAndNormalizePullRequests;

describe('Pull requests handler', async () => {
  const mockedPullRequestsValue = [];

  before(async () => {
    // setup the mock fn
    mockedFetchAndNormalizePullRequests = mock.fn(async () => mockedPullRequestsValue);
    
    // mock the module and provide the stub for the method
    mock.module('../../services/pull-requests.service.js', {
      fetchAndNormalizePullRequests: mockedFetchAndNormalizePullRequests,
    });

    // import (and assign to the variable) the function AFTER mocking the method on the module
    ({ getAllPullRequests } = import('../../handlers/pull-requests.handler.js')); 
  })

  beforeEach(() => {
    mockedPullRequestsValue.length = 0; // clear the mocked values
  })

  after(() => {
    mock.restoreAll();
  })

  test('Your test', async () => {
    mockedPullRequestsValue.push({yourObject: 'your value'}) // setup the return value you want
    await getAllPullRequests(/* params */); // call your function
    
    /* make your asserts */

  })
})

Collectives™ on Stack Overflow

Typescript Node test cannot redifine property?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related