I am trying to write a simple unit test for a utility function in my Firebase cloud functions. The test suite fails showing an error with the “firebase-functions” package, however I am not using and or testing anything Firebase related in this test. Not sure why the Vitest is failing. Any help is greatly appreciated.

Function being tested:

/**
 * Post a tweet to the user's Twitter account.
 *
 * @param {string} authHeader
 * @param {Tweet} tweet
 * @return {*}  {Promise<string>} The tweet ID.
 */
export async function postTweet(authHeader: string, tweet: Tweet): Promise<string> {
  const response = await axios
    .post(
      'https://api.twitter.com/2/tweets',
      { text: tweet.text },
      {
        headers: {
          Authorization: authHeader,
          'Content-Type': 'application/json',
        },
      }
    )
    .catch((error) => {
      const twitterError = isTwitterError(error);
      if (twitterError) {
        throw twitterError;
      }

      throwUnknownAxiosError(error, 'Failed to post tweet');
    });

  logger.info('Tweet posted', { responseData: response.data });
  return response.data.data.id;
}

Test file:

import { describe, it, expect, vi, beforeEach, MockedFunction } from 'vitest';
import axios from 'axios';
import { postTweet } from './twitter';
import { Tweet, TweetType } from './models/twitter';
import { Timestamp } from 'firebase-admin/firestore';

vi.mock('axios');

describe('postTweet', () => {
  const mockAuthHeader = 'Bearer mock-token';
  const mockTweet: Tweet = {
    text: 'Test tweet',
    id: 'tweet1',
    createdAt: Timestamp.fromDate(new Date()),
    lastSentAt: Timestamp.fromDate(new Date()),
    type: TweetType.Starting,
    userId: 'user123',
  };

  beforeEach(() => {
    vi.resetAllMocks();
  });

  it('throws an error if a duplicate tweet is sent', async () => {
    const mockError = {
      response: {
        data: {
          errors: [{ code: 187, message: 'Status is a duplicate.' }],
        },
      },
    };
    (axios.post as MockedFunction<typeof axios.post>).mockRejectedValueOnce(mockError);

    await expect(postTweet(mockAuthHeader, mockTweet)).rejects.toThrow('Status is a duplicate.');
  });
});

Error being thrown:

 FAIL  src/twitter.spec.ts [ src/twitter.spec.ts ]
Error: Missing "./lib/common/providers/identity" specifier in "firebase-functions" package
 ❯ e node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:45978:25
 ❯ n node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:45978:627
 ❯ o node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:45978:1297
 ❯ resolveExportsOrImports node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:46599:18
 ❯ resolveDeepImport node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:46622:25
 ❯ tryNodeResolve node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:46387:16
 ❯ ResolveIdContext.resolveId node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:46137:19
 ❯ PluginContainer.resolveId node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:48952:17
 ❯ TransformPluginContext.resolve node_modules/vite/dist/node/chunks/dep-DG6Lorbi.js:49112:15

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