jest: Jest mock module failed when mocking mongoose model object

Problem mocking a mongoose model Object with the following error.

  ● Test suite failed to run

    TypeError: Cannot create property 'constructor' on number '1'

      at ModuleMockerClass._generateMock (node_modules/jest-mock/build/index.js:457:34)
      at Array.forEach (native)
      at Array.forEach (native)
      at Array.forEach (native)

repo with reproduction code node - v6.9.3 yarn - v0.18.1 npm - 3.10.10 OS - macOS Sierra

About this issue

Original URL
State: closed
Created 7 years ago
Reactions: 14
Comments: 22 (12 by maintainers)

Commits related to this issue

Fixes issue #3073. Typechecks prototype before assignment. Fixes interaction with mongoos — committed to hluedeke/jest by deleted user 6 years ago

Most upvoted comments

I have the same issue, how can fix it ? @cpojer @thymikee

Dimatymoshchenko on Aug 31, 2018

I had a look into this issue and it seems that Mongoose creates an object with a key called prototype and sets it to 1: https://github.com/Automattic/mongoose/blob/master/lib/schema.js#L464

It turns out that Jest doesn’t like this. I’ve created a minimal repro of the problem here: https://github.com/smably/jest-prototype-test

Adding another check for typeof mock.prototype === 'object' does seem to fix this issue (thanks @hluedeke!). If no objections, I’d also be happy to open up a PR with that fix.

smably on Mar 4, 2019

@hluedeke seems like the --fix is added to jest and not eslint… You can run yarn lint --fix and it should be fixed

SimenB on Mar 4, 2019

If no objections, I’d also be happy to open up a PR with that fix.

@smably I’d be eternally grateful! I forked and updated it…but can’t get all the jest tests to pass 😒 (even with periodic pulls)…so I’ve been hesitant to submit it

hluedeke on Mar 4, 2019

+1 I have the same issue with built-in auto-mock…, but I just manually mock directly upon the method I want to stub.

leoyli on May 26, 2018