This tests that SVGTextContentElement.getSubStringLength() handles out-of-range charnum and nchars parameter values correctly.
The test consists of 5 sub-tests, which test the different combinations of values passed to SVGTextContentElement.getSubStringLength(). 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.
Run the test. No interaction required. The test relies on support for SVG Fonts.
The test is passed if all 5 rectangles are green.