Test Assumptions

The tests make a number of assumptions of the user agent, and new tests can freely rely on these assumptions being true:

* The device is a full-color device. * The device has viewport dimensions of at least 800px by 600px. * The UA imposes no minimum font size. * The medium font-size computes to 16px. * The canvas background is white. * The initial value of color is black. * The user stylesheet is empty (except where indicated by the tests). * The device is interactive and uses scroll bars. * The HTML div element is assigned display: block;, the unicode-bidi property may be declared, and no other property declarations. <!-- unicode-bidi: isolate should be required; we currently don't assume this because Chrome and Safari are yet to ship this: see https://bugs.chromium.org/p/chromium/issues/detail?id=296863 and https://bugs.webkit.org/show_bug.cgi?id=65617 --> * The HTML span element is assigned display: inline; and no other property declaration. * The HTML p element is assigned display: block; * The HTML li element is assigned display: list-item; * The HTML table elements table, tbody, tr, and td are assigned the display values table, table-row-group, table-row, and table-cell, respectively. * The UA implements reasonable line-breaking behavior; e.g., it is assumed that spaces between alphanumeric characters provide line breaking opportunities and that UAs will not break at every opportunity, but only near the end of a line unless a line break is forced.

Tests for printing behavior make some further assumptions:

* The UA is set to print background colors and, if it supports graphics, background images. * The UA implements reasonable page-breaking behavior; e.g., it is assumed that UAs will not break at every opportunity, but only near the end of a page unless a page break is forced.