The Diddy trial’s 16th day of testimony took place Wednesday … but, it wasn’t the sweet 16 he may have hoped for — ’cause the woman who testified painted a pretty scary picture of him.

Bryana Bongolan — Cassie‘s friend and a fashion designer — took the stand Wednesday … and, she testified about the time Diddy allegedly dangled her off a balcony while they were either smoking or about to smoke a blunt at Cassie’s place.

Bongolan says Diddy held her off of the high-rise and yelled, “You know what the f*** you did” … before she says he pulled her back up and slammed her into the furniture.

She also testified about another alleged incident where she says Diddy threw a knife at Cassie … and Cassie threw one back in self-defense.

Bryana talked a lot about drugs … claiming Puffy provided some to her — and, she bought some for him and Cassie as well.

Despite the intensity of her testimony, Diddy’s defense team did an impressive job countering … asking for specific details from each incident that it seemed Bongolan just couldn’t remember.

Before Bongolan took the stand, video expert Frank Piazza testified about the authenticity of the infamous Cassie beating video … and, he says it hasn’t been altered at all, diving into all the high-tech language to explain why.

While it’s mostly standard stuff, Piazza also revealed he cleaned up the audio of 10 alleged sex tapes for the prosecution … which it seems like they will roll out in the coming weeks of the trial.