Yeah I read the bit about an engine test.
It all seems rather odd. I'd think it obvious to "perform a volatile procedure" away from non-hardened buildings. If it was sloppy procedures then they didn't learn from the numerous launch pad events on either side of the iron curtain during the cold war - and a few since then.
Even in this Atlas explosion the blast seems
reasonably localised.
It could have been a test of the mooted larger Shahab 4,5 or 6 but the same lessons would hold true, unless they seriously miscalculated the potential blast.