chore: attach mongoMemoryServer to db and destroy in tests (#5326)

* chore: attach mongoMemoryServer to db and destroy in tests

* bump mongodb-memory-server to 9.x

---------

Co-authored-by: Paul Popus <paul@nouance.io>

test/dataloader/int.spec.ts

@@ -1,11 +1,9 @@
 import type { Payload } from '../../packages/payload/src/index.js'
-
 import { getPayload } from '../../packages/payload/src/index.js'
 import { devUser } from '../credentials.js'
 import { NextRESTClient } from '../helpers/NextRESTClient.js'
 import { startMemoryDB } from '../startMemoryDB.js'
-import configPromise from './config.js'
-import { postDoc } from './config.js'
+import configPromise, { postDoc } from './config.js'
 
 let restClient: NextRESTClient
 let payload: Payload
@@ -28,6 +26,12 @@ describe('dataloader', () => {
     if (loginResult.token) token = loginResult.token
   })
 
+  afterAll(async () => {
+    if (typeof payload.db.destroy === 'function') {
+      await payload.db.destroy()
+    }
+  })
+
   describe('graphql', () => {
     it('should allow querying via graphql', async () => {
       const query = `query {