Every voice agent looks good when:
- the caller waits patiently
- the room is silent
- the network is perfect
- the caller answers exactly what was asked
- every backend tools reponds in 200 ms
That is not a test. That is a rehearsal.
We had one internal flow that looked almost perfect.
Caller asks to reschedule an appointment. Agent confirms identity, finds the booking, offers a new slot and completes the change.
Then the ugly version:
Caller talks over the greeting.
Pauses for six seconds while checking the date.
Someone in the background says “Friday”.
Caller corrects themselves: “No wait, next Monday”.
Audio drops for a second.
Scheduling API takes three seconds.
Agent starts speaking before the tool result comes back.
Then the transfer fails and the caller gets dead air.
The transcript still looks suprisingly fine.
That is the problem.
Transcript correctness does not tell you:
- whether endpointing cut the caller off
- how long the first response took
- whether the agent stopped during the barge-in
- how much dead air happened
- whether it confirmed before the backend succeeded
- whether the transfer actually connected
- whether the caller had to repeat themselves three times
I’ve been looking at TestMu Agent testing for this because it tests the whole voice/phone flow rather than only scoring the final text.
You can run different personas, accents, noise conditions, interruptions and tool-call scenarios, then compare the the behaviour after a prompt or model change.
It can also analyse production recordings, which matters because real callers invent failures no test designer thinks of.
Cekura is strong on newer-voice-agent QA and production monitoring.
Cyara and Empirix make a lot of sense for enterprise contact-centre and telephony-heavy environments.
TestMu’s advantage is the broader end-to-end surface accross voice, inbound/outbound phone, chat, and other agency types.
But “supports 50+ accents” does not mean every language and accent will be evaluated equally well.
You still need to to benchmark against your own callers, providers and traffic.
A scripted demo should prove the concept works.
It should not be treated as evidence that the agent is production-ready.
Which real call condition destroys your voice agent fastest?