Grammar Quiz #11 brings up the old problem of too much distance between the modifier and the word it modifies. “Only” needs to be close to ‘testified’ to make it clear that they weren’t chanting or twerking or doing the Funky Chicken. Make it, “Testified only about their . . .”
Dr. John’s Grammar Quiz #12: Can you spot the glaring grammatical error in this sentence? “No bond firm should feel any pressure simply because they were called by the City Budget Director.”