Testing Retell

You built your agent on Retell. Testzilla is the testing layer you plug in beside it — not a platform you migrate to. It is vendor-neutral but vendor-interactive: it drives your real Retell agent the way your users do, so the results reflect what you actually shipped.

Retell is Testzilla’s most complete integration: it is the one provider that supports all four connection types.

What you can test

Surface	Connection type	What it exercises
Phone line	Phone	Real inbound call (Testzilla dials your agent): telephony, ASR, LLM, TTS, IVR, transfers. Outbound coming soon.
Chat widget on your site	Web Chat	The real Retell widget in a real browser, via the DOM
Browser voice button	Web Voice	A real WebRTC session via Retell’s web-call SDK
Agent logic, fast and cheap	LLM Chat	The Retell chat agent directly over text

Why teams test Retell with Testzilla

No rebuild

Point Testzilla at your existing Retell agent ID and phone number. Nothing about your Retell setup changes.

Cheap regression gate

LLM Chat is 1 credit per round-trip — run it on every deploy to catch prompt and tool-call regressions before they reach a phone call.

Test the whole stack

Only Retell gives you all four channels, so you can verify the same scenario from the LLM up through the live phone line.

Visual checks on the widget

Web Chat captures screenshots of the Retell widget at each turn, so you can spot rendering breaks the transcript would miss. See Reading Web Chat Results.

Get started

1. Have your Retell API key and agent ID ready (chat must be enabled in the Retell dashboard for LLM Chat).
2. Follow the guide for the surface you care about: phone, web chat, web voice, or LLM.
3. To benchmark the same tests across several Retell channels at once, run a suite.

Tip

Want it automated? Drive Retell tests from CI via the API, or from an AI agent via MCP.

Related providers

Testing Vapi Phone and Web Voice for Vapi assistants.

Testing ElevenLabs Web Voice for ElevenLabs Conversational AI.