Add test docs and fix some docs problem.

[KomachiSion]

What is the purpose of the change

XXXXX

Brief changelog

XXXXX

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a GITHUB_issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a GITHUB issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like Fix UnknownException when host config not exist #XXX. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Test your code locally by running npm run build, and make sure it works as expected.
• Make sure no files under build directory is added.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.