mongoose jest memory leak

[sibelius]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
the heap usage keeps increasing when using mongoose

If the current behavior is a bug, please provide the steps to reproduce.

You can reproduce this bug using this repo https://github.com/graphql-compose/graphql-compose-mongoose from @nodkz

run jest --logHeapUsage

heap usage will keep increasing:

You can also run with jest --detectLeaks --detectOpenHandles and check that there are some open handles that keeps Jest from exiting:

What is the expected behavior?
The expect behavior is to clean up the heap usage after each test

Please mention your node.js, mongoose and MongoDB version.
mongodb version: 3.x.x and 4.x.x
mongoose 5.2.6
node 8.x.x and 10.x.x

related to #2874

more info here jestjs/jest#6787

I've tried to add this to afterEach, afterAll and it did not help

#2874 (comment)

mongoose.connections.forEach(connection => {
  const modelNames = Object.keys(connection.models)

  modelNames.forEach(modelName => {
    delete connection.models[modelName]
  })

  const collectionNames = Object.keys(connection.collections)
  collectionNames.forEach(collectionName => {
    delete connection.collections[collectionName]
  })
})

const modelSchemaNames = Object.keys(mongoose.modelSchemas)
modelSchemaNames.forEach(modelSchemaName => {
  delete mongoose.modelSchemas[modelSchemaName]
})

is there any place where mongoose keep references? that is not garbage collected properly?

[sibelius]

afterAll worked well to reduce memory leak in mongoose

we fixed the rest of leak mocking graphql-redis-subscriptions

[murbanowicz]

What did you add exactly to the afterAll?