When we talk about carriers testing smartphones, what exactly do we mean? They’re going to look for how the phones interact with their network, obviously, but they’re also interested in general performance and stability. T-Mobile just shared a look at one of the tools it has at its disposal for speeding-up that kind of testing, a smartphone-tapping robot that simulates normal user interaction.

This robot spends its days tapping away at on-screen elements and capacitive buttons while a watchful camera overhead tries to spot any anomalies. If an app crashes or freezes when it gets an input it’s not expecting, or at the wrong time, this robot wants to catch it.

Of course, just because there’s a robot doing all the grunt work doesn’t mean that the human element is unneeded; T-Mobile’s engineers have to tell this custom robot what to do, and interpret the results of the tests they have it perform. Sure, they might not catch everything (as plenty of us can attest to), but evaluating phones in this semi-automated manner supposedly lets the carrier catch more bugs than it would with a fully human-based search.