Tests failing

## To reproduce

```sh
npm test
```

## What should happen

Tests should pass.

## What actually happens

Three tests fail.

## Relevant output

```sh
3 failing

1) OCSP Stapling Provider .check() should validate google.com:
Uncaught Error: Bad OCSP response status: unauthorized
at Object.parseResponse (lib/ocsp/utils.js:68:11)
at Object.verify (lib/ocsp/verify.js:52:22)
at lib/ocsp/check.js:38:12
at done (lib/ocsp/utils.js:26:7)
at IncomingMessage. (lib/ocsp/utils.js:46:7)
at endReadableNT (_stream_readable.js:1204:12)
at processTicksAndRejections (internal/process/task_queues.js:84:21)

2) OCSP Cache should cache ocsp response:
Uncaught TypeError: Cannot read property 'getPeerCertificate' of null
at Agent.handleOCSPResponse (lib/ocsp/agent.js:70:25)
at TLSSocket. (lib/ocsp/agent.js:52:17)
at TLSSocket._finishInit (_tls_wrap.js:916:8)
at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:686:12)

3) OCSP Cache "after each" hook:
Uncaught Error: unsupported certificate purpose
at TLSSocket.onConnectSecure (_tls_wrap.js:1473:34)
at TLSSocket._finishInit (_tls_wrap.js:916:8)
at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:686:12)
```

## Update (2023-07-05):

- Above results were with Node 12.16.2.
- With Node 18.16.0, On the first two failures are shown.

Run npm test first, then trace the reported failures through lib/ocsp/utils.js, lib/ocsp/verify.js, lib/ocsp/check.js, and lib/ocsp/agent.js. Compare behavior on the Node.js versions mentioned in the update; done means the three reported tests and the after-each hook pass.

Written by the indexing model from the issue text.