Summarized test results:
HTML5, dir isolation

To run the test, or to see detailed, per character, results, click on the link in the left-most column. To see detailed results click on a row and look just above the table.

Where the instructions tell you to look for red strokes, these strokes should be clearly discernable behind the black text of the test – ignore any anti-aliasing 'glow'.

Key: pass fail partially successful

These tests check whether user agents apply isolation around an element where the dir attribute is used, and treat it as a neutral character.

Section The dir attribute says that when values of dir are rtl or ltr "contents of the element are explicitly directionally isolated".

Section of the HTML5 specification, part of the section Requirements relating to the bidirectional algorithm, says "The following elements and attributes have requirements defined by the rendering section that, due to the requirements in this section, are requirements on all user agents (not just those that support the suggested default rendering)". Section 10.3.5 Bidirectional text expresses the expected rendering in terms of CSS.

Basic tests

Other tests

These tests look at edge cases.

With CSS shim

The following tests are the same as those in the previous section, but use the following CSS shim to produce the needed isolation.

[dir='ltr'], [dir='rtl'] {
  unicode-bidi: -webkit-isolate;
  unicode-bidi: -moz-isolate;
  unicode-bidi: -ms-isolate;
  unicode-bidi: isolate;