This tests that methods on the SVGTextContentElement interface that take an index to a character or a number of characters actually interpret these as indexes to or numbers of UTF-16 code units. To test this, a character from outside the Basic Multilingual Plane (U+10000; LINEAR B SYLLABLE B008) is used in a text string. This character is stored in UTF-16 as a surrogate pair.

The test consists of two sub-tests, which test those methods on the SVGTextContentElement interface which do not rely on rendering. The result of each sub-test is shown as a small rectangle: black indicates that the sub-test did not run, red indicates that the sub-test failed and green indicates that the sub-test succeeded.