This test validates that the font element's horiz-adv-x is used as the default glyph's advance when there is no glyph advance specified. All fonts have a units-per-em of 1000.
The first row shows a layout with a default advance of 1000. Glyphs have no advance so the 1000 default should be used.
The second row shows a layout with a default advance of 2000. Glyphs have no advance so the 2000 default should be used.
The last row shows a layout with a default advance of 0. Glyphs have a specified advance so the 0 default should be ignored.
Blue reference markers show the expected glyph positions.
Run the test. No interaction required.
There are three subtests. The test is passed if for each subtest there is labelling text on the left and on the right, a series of black squares whose lower-left corner aligns with the centre of the corresponding small, pale blue square as shown in the reference graphic.