Self signed certificate issue

Hello everyone and thank you for reading.
I'm testing an API (Internal) that calls another API (external), and processes the results.
When I test methods that don't use the external, everything is fine.
When I call it via postman, the problematic method it works perfectly.
But, when I call it via SuperTest I get
```
Error: self signed certificate
at TLSSocket.onConnectSecure (_tls_wrap.js:1514:34)
at TLSSocket.emit (events.js:400:28)
at TLSSocket._finishInit (_tls_wrap.js:936:8)
at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:708:12) {
code: 'DEPTH_ZERO_SELF_SIGNED_CERT',
```
I've tried setting
`process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0';`
and
```
"jest": {
"testEnvironment": "node"
}
```
without success.

Any ideas? I don't know what to do next.

Thank you all again.