The font for this test case defines a Mark Positioning feature in its Glyph Positioning table. The feature uses a MarkToBase Attachment Positioning Subtable for placing Ethiopic diacritics on top of a base glyph. If your text rendering engine is correct, the dots (which indicate “long vowel”, “long consonant”, and “long consonant plus long vowel”) should be placed on top of the base glyph (the syllable “la”). If the dots appear to the right of the base glyph, or if they are missing entirely, it’s a sign that your text rendering system is broken.