Need explanation of how to run tests in rest-api-spec test guide

[chen-ni]

The rest-api-spec tests guide is confusing because after all the explanations of the test file structure, it doesn't tell us how to actually RUN an individual test or a test suite.

Luckily for me, I happened to run into this comment that explains how to run such a test.

It would be better if we could add an explanation of how to run tests (or a link to some doc located elsewhere) to the guide. It won't be much work but would save a lot of time for the developers.

I'd be glad to create a PR for this.

[elasticmachine]

Pinging @elastic/es-delivery (Team:Delivery)

[mark-vieira]

We have a whole separate README specifically about test execution. It might be as simple as just linking to this section from the rest-api-spec guide.

[chen-ni]

@mark-vieira Thanks, I'll create a PR adding the link :)