@moollaza  n.b. You're really good at noticing the constructions I found awkward and suggesting better ones.  Much appreciated.

 >"This helps others ... code. " -- not quite sure what you mean here

Would it be more clear if it said "This helps the community quickly understand..."?  The idea being: the better your test suite, the easier it is for someone else to understand what is going on.  I was trying to keep this as a sort of general guideline for "why people bother writing tests" before focusing on "so what about testing for DDH" in the next paragraph.