@fakekamrankhan Both .listen() and .close() receive an optional callback, to properly wait for those operations to complete. You need to manually provide those callbacks, so that Jest waits for those operations.

beforeAll((done) => {
  port = 3000;
  server = new express().listen(port, done);
});

afterAll((done) => {
  server.close(done);
})

Thanks for the response!

That is one of the many variations I did try in my troubleshooting to close off functions before Jest prematurely exits but it still complains of memory leak. I just tried the code you mentioned and it is still throwing the same error.

Both of these triggers Jest to complain of memory leak:

beforeAll((done) => {
  port = 3000;
  server = new express().listen(port, done);
});

afterAll((done) => {
  server.close(done);
});

beforeAll( async () => {
  port = 3000;
  server = await new express().listen(port, done);
});

afterAll( async () => {
  await server.close();
})

Any updates on this?

Still the same problem! :(

Any update on this issue?

Given the last reproduction example sent by @fakekamrankhan (which only involves express). Seems unlikely that this is an issue with this library.

@jonathansamines I'm actually not sure that that's the case. I was able to reproduce this issue with Koa since I was passing it an instance of the (previously started) server.

I've submitted PR #651 which completely fixed my issue.

In case you guys haven't looked in the jest issues, it looks like this is occurring because one of the modules you're using is mutating a native node module, eg. http, https, etc. I drove myself crazy hunting down this issue in my integration tests; the culprit turned out to a library called follow-redirects. It was mutating the http and https modules.

In case you guys haven't looked in the jest issues, it looks like this is occurring because one of the modules you're using is mutating a native node module, eg. http, https, etc. I drove myself crazy hunting down this issue in my integration tests; the culprit turned out to a library called follow-redirects. It was mutating the http and https modules.

Interesting. Is it solved in follow-redirects, or is there an issue opened on them?

Still an issue in 2021 👎

In case you guys haven't looked in the jest issues, it looks like this is occurring because one of the modules you're using is mutating a native node module, eg. http, https, etc. I drove myself crazy hunting down this issue in my integration tests; the culprit turned out to a library called follow-redirects. It was mutating the http and https modules.

I don't think this is the bottom of it. I've tried the most basic setup (empty project with express, jest and supertest) and --detectLeaks fails for me still. See #520 (comment).

For anyone seeing this now, I do not see a handle leaking in my supertest jest tests to which I pass an already constructed express app instance.