Thanks for the consideration, Stuart. According to my book, the event took place in the Third Samnite War (so actually early 3rd Century, not 4th). The Romans were bent on avenging their humiliation at the Caudine Forks a generation earlier.
293 BC the Romans defeated a Samnite army outside the Samnite city of Aquilonia, the prepared for an assault on the gate and walls with ladders:
"Orders were issued for scaling ladders to be reared against the walls in all directions and an approach made to the gates under a shield roof." (i.e., testudo, see below)
Here's the actual Latin text:
"ipse scalas ferri ad muros ab omni parte urbis iussit ac testudine ad portas successit."
I usually translate much more literally (can't stand it when authors take liberties with the text): "He himself [the consul] ordered ladders to be brought to the wall from every part of the city and he approached toward the gates by means of a testudo." The Latin word here, testudine, is the ablative case of testudo indicating use of something (Ablative of Means/Instrument).
Earlier on in 10.41, we also have the assault of L. Cornelius Scipio Scapula on the gate (I think from another side of the city?):
"secuti alii testudine facta in urbem perrumpunt deturbatisque Samnitibus quae circa portam erant muri occupauere." "Others following, with a testudo made, burst into the city and -with the Samnites confused (?) - occupied the walls which were around the gate." (the second part is much rougher than the first part mentioning the testudo, but you get the point....)
One could argue that Livy, writing hundreds of years later, doesn't know what he's talking about, or is inserting anachronisms. But the source says what it says. Anyway, I think it'd be kinda cool to have this continuity between the Mid Republican Maniple rule and the later Legion rule.