Disclaimer: I'm the author of gabbi.

It's great to see more and more API testing tools that use a format intending to be readable.

I personally think YAML is a bit more readable for humans so that's what I used when I created gabbi. Here's a similar test to one of the examples from apitest:

  tests:

  - name: httpbin post
    POST: https://httpbin.org/post
    verbose: true
    request_headers:
      content-type: application/json
    data:
      foo1: bar1
      foo2: Bar2

    response_headers:
      content-type: application/json
    response_json_paths:
      $.json.foo1: bar1
      $.json.foo2: Bar2
      $.headers.Host: httpbin.org

https://github.com/cdent/gabbi