Summarized test results:
HTML5, the ruby element and its children

These tests check whether user agents support styling and basic default positioning of markup based on ruby markup, including the elements ruby, rb, rt, and rtc. 

Tests are provided for the range of ruby-related elements specified in the W3C HTML 5.3 specification. The WhatWG HTML specification omits the rb and rtc elements.

They do not test the features of the CSS Ruby module, just whether the structure of the ruby markup is recognised by the browsers, and whether those minimal features needed to position the ruby text are available without CSS styling.

Styling

These tests check that the browser is able to identify and style the various elements that make up the ruby content. Where there are multiple tests, each test uses a different approach to markup, eg. both start and end tags, or just start tags.

Needless to say, markup styles that omit the rb element tags don't allow the rb content to be styled.

Single-sided ruby position

These tests are exploratory. The HTML spec doesn't actually indicate how ruby bases and annotations should be positioned relative to each other, it is concerned with associating the right base with the right annotation(s). Expected positioning is not specified in the part of the spec that describes the ruby elements, nor in the Rendering section of the spec. However, one can reasonably expect that in simple cases annotations are positioned above bases, by default. That is what these tests set out to explore.

Double-sided ruby

These tests are exploratory. As for the previous section, the HTML spec doesn't actually indicate how ruby bases with multiple annotations should be positioned relative to each other. However, one can reasonably expect that annotations are vertically stacked above bases, by default. That is what these tests set out to explore. (CSS would need to be used to position multiple annotations one over and one below.)