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Test a Phone Number

If your agent lives on a phone number, this is the highest-fidelity test you can run. Testzilla dials in to your agent and runs a real phone call through your telephony provider (Retell or Vapi), exercising the whole voice pipeline — telephony, ASR, LLM, TTS — exactly as a real caller would experience it, including IVR routing, hold music, and transfers.

Direction is named from your agent’s (the agent under test) point of view:

  • Inbound — your agent receives the call (available today). Testzilla dials your agent’s number and runs the tester on the call. This guide covers inbound.
  • Outbound — your agent places the call (available today). Testzilla provisions a dedicated number per outbound test; your agent dials it, a predeployed Testzilla agent answers and runs the call, and the transcript is scored afterward. See Phone Testing: Inbound vs Outbound for the full comparison — this guide covers inbound.

Before you start

Section titled “Before you start”
  • A Testzilla account (sign up).
  • An agent deployed on an inbound phone number with Retell or Vapi.
  • The agent’s phone number, and your provider credentials (API key and agent ID).

Set it up

Section titled “Set it up”

  1. Create a project

    In the web app, create a project to group this agent’s channels and tests. (Or skip ahead and let TZ Console do all of this from a plain-language prompt.)

  2. Add a Phone channel

    In the project, click + Channel and pick the Phone adapter. Phone channels default to Retell; switch to Vapi if that is where your agent lives.

    Fill in:

    • Provider — Retell or Vapi.
    • The inbound phone number — your agent’s number, the one Testzilla will dial.
    • Provider credentials — API key and agent ID.

  3. Write a test

    Add a test describing the scenario and the pass/fail criteria in plain language, for example: “Caller asks to book a haircut for Saturday. The agent must confirm the day and time and must not ask for a card number.”

  4. Run it

    Click Run, choose how many iterations, and optionally schedule it. Testzilla dials your agent and runs the conversation. Track it on the Queue page.

  5. Read the result

    Open the finished run for the transcript, the pass/fail verdict, a score, an analysis, and the data collected during the call. Every section has a Copy button.

Next steps

Section titled “Next steps”