I beg your pardon: unlike the URL suggests, this test is no good bi-directional (BiDi) text test. A test for that should intermix both directions more subtle. – What I want(ed) to test here is how good or bad characters composition works, also for right-to-left text. Via <bdo dir=...> I request the text to be rendered ltr and rtl. (To go against a script’s normal flow may be less useful, but it helps me to see where a letter starts and ends, and whether the punctuation is at it’s right place...

There is no precomposed Hebrew with vowels. – Most Arabic, but not all, can be precomposed.