"leaking due to improper teardown" in Jest - mysql

Question

I am trying to write tests for an express API that uses Axios and is connected to a mySQL database. I am getting the following error when I run my tests in Jest:
A worker process has failed to exit gracefully and has been force exited. This is
likely caused by tests leaking due to improper teardown. Try running with --
detectOpenHandles to find leaks. Active timers can also cause this, ensure that
.unref() was called on them.
After running detectOpenHandles, I get the following:
Jest has detected the following 3 open handles potentially keeping Jest from exiting:
● TCPWRAP
15 |
16 |
> 17 | const connection = mysql.createConnection(process.env.MYSQL_CONNECTION)
| ^
18 |
19 | /**
20 | * #swagger
at new Connection (node_modules/mysql2/lib/connection.js:45:27)
at Object.createConnection (node_modules/mysql2/index.js:10:10)
at Object.<anonymous> (src/users/router.js:17:26)
at Object.<anonymous> (src/index.js:9:25)
at Object.<anonymous> (src/server.js:1:13)
at Object.<anonymous> (__tests__/app.test.js:3:13)
● TCPSERVERWRAP
3 |
4 |
> 5 | app.listen(serverPort, () =>
| ^
6 | console.log(`API Server listening on port ${serverPort}`)
7 | );
8 |
at Function.listen (node_modules/express/lib/application.js:618:24)
at Object.<anonymous> (src/server.js:5:5)
at Object.<anonymous> (__tests__/app.test.js:3:13)
● TLSWRAP
16 | const getMgmtApiJwt = async () => {
17 | try {
> 18 | const resp = await axios(newRequest);
| ^
19 | return resp.data
20 | } catch (e) {
21 | console.log("did not work");
at RedirectableRequest.Object.<anonymous>.RedirectableRequest._performRequest (node_modules/follow-redirects/index.js:279:24)
at new RedirectableRequest (node_modules/follow-redirects/index.js:61:8)
at Object.request (node_modules/follow-redirects/index.js:487:14)
at dispatchHttpRequest (node_modules/axios/lib/adapters/http.js:202:25)
at httpAdapter (node_modules/axios/lib/adapters/http.js:46:10)
at dispatchRequest (node_modules/axios/lib/core/dispatchRequest.js:53:10)
at Axios.request (node_modules/axios/lib/core/Axios.js:108:15)
at axios (node_modules/axios/lib/helpers/bind.js:9:15)
at getMgmtApiJwt (src/users/controller.js:18:24)
at Object.<anonymous> (__tests__/app.test.js:182:24)
What can I try next?

Answer 1

Implement a global tear down setup. That should fix this issue.
Take a look at Fiehra's answer here: jest and mongoose - jest has detected opened handles