fix supertest app.test.ts example

[lukeymyuan]

Why

The below unit tests do not fail when endpoint returns 404
We either use expect function or throw when check fails https://github.com/ladjs/supertest#expectfunctionres-

- await agent.get('/').expect(({ status }) => status !== 404);
+ await agent.get('/').expect(({ status }) => expect(status).not.toBe(404));

What

Modify unit test
Add usage message when argument is not received

[changeset-bot]

🦋 Changeset detected

Latest commit: 865be0b

The changes in this PR will be included in the next version bump.

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[72636c]

🙇 thanks a bunch!