Jest did not exit one second after the test run has completed

Goals

Trying to close Realm instance after each unit test.

Expected Results

Everything shutdown nicely.

Actual Results

Test succeeds but Jest complains there are asynchronous operations that weren't stopped, then the Jest process will hang.

Steps to Reproduce

1. Minimal realm set up
2. Open the database during one test
3. Close the database once done.

Code Sample

https://github.com/simophin/realm-close-issue

$ npm install && npm run test

This is the result I got:

npm run test

> testrealm@1.0.0 test /Users/***/Temp/testrealm
> jest ./src

 PASS  src/__tests__/realm-tests.ts
  realmTest
    ✓ should exist (17 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.339 s, estimated 2 s
Ran all test suites matching /.\/src/i.
Jest did not exit one second after the test run has completed.

This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with `--detectOpenHandles` to troubleshoot this issue.

Also, if I add --detectOpenHandles to jest, the test will succeed, without the complain, but still hang. If I added --detectOpenHandles --forceExit to jest, the test will succeed, without the complain, and terminate successfully.

This does not happen in realm-js 5.0.x, only after we upgraded to 6.0.

Version of Realm and Tooling

• Realm JS SDK Version: 6.0.2
• Node or React Native: Node 10.21.0
• Client OS & Version: Mac OS
• Which debugger for React Native: None