ecko
Mock mode
With no provider configured, ai answers from a deterministic mock instead of failing. See Mock mode in Getting Started for the introduction; this page is the detail that matters once you are building.
What mock mode replaces
The provider call. Nothing else.
| still runs for real | replaced by a mock |
|---|---|
@tool functions - your actual code | the provider's choice of tool |
| Boolean contracts | string contracts (they always pass) |
| Coercion to the requested type | the model's reply |
| Retry and backoff | |
| Budget counting | |
| Tracing |
That split is why mock mode is worth trusting: the machinery around the call is exercised exactly as it will be in production, so a schema mistake, a broken tool signature or a missing branch fails offline.
Determinism
The same program produces the same bytes every run. This is what makes an ai pipeline testable at all - ecko test forces mock mode, so a test can assert on output.
| call | mock result |
|---|---|
ai "..." | [AI Mock] <prompt> |
ai[Int] / ai[Float] | 42 / 42.0 |
ai[Bool] | true |
ai[Enum] | the first variant |
ai[Struct] | each field's mock |
ai[json<List<T>>] | a one-element list |
ai "..." on img | [AI Mock] <prompt> [image WxH] with the real dimensions |
Tools in mock mode
The loop is deterministic rather than absent: it invokes every tool named in the prompt, passes the prompt as the argument, and returns the last tool's result. Enough to prove the wiring works.
One deliberate difference: a failing tool throws offline, where live mode feeds the error back to the model. Live, the model is the recovery mechanism; offline, you are, so the failure surfaces instead of being swallowed.
What it cannot tell you
Whether the answer is any good. Mock mode validates structure, not content. A prompt that produces confident nonsense from a real model produces a schema-perfect 42 offline.
Two things close that gap: boolean contracts, which are real checks that run identically on and offline, and running against a provider before you ship. Mock mode makes the program trustworthy; it says nothing about the model.
Turning it off
Set ECKO_API_KEY. ecko test ignores it by design - a test run never spends money.