---
title: "ADR-079: First-party fakes for Completion, Vision and Budget services"
manual: "TYPO3 LLM Extension"
version: "0.35"
permalink: "https://docs.typo3.org/permalink/netresearch/nr-llm:adr-079@0.35"
source: "Adr/Adr079FirstPartyCompletionVisionBudgetFakes.rst"
modified: "2026-09-16T22:09:16+00:00"
---

# ADR-079: First-party fakes for Completion, Vision and Budget services

-   *Status:* Accepted
-   *Date:* 2026-07-17
-   *Authors:* Netresearch DTT GmbH

## Context

[ADR-073](https://docs.typo3.org/permalink/netresearch/nr-llm:adr-073@0.35) shipped maintained, first-party test doubles for
the tool-calling and embedding feature services under the runtime-autoloaded
`Netresearch\NrLlm\Testing\` namespace, because consumers were hand-rolling
doubles that fatal the moment the interface grows. It deliberately deferred
the remaining feature interfaces: "Other feature interfaces (completion,
vision, translation) gain a first-party fake only when a consumer needs one."

That consumer now exists. `nr_repurpose` (podcast/diagram/story generation)
consumes `CompletionService` and `VisionService` and gates image/speech
spend through `BudgetServiceInterface` — and its hand-written
`BudgetServiceInterface` double is exactly the one that broke across
consumers when `check()` gained its `?LlmConfiguration` parameter (the
0.20 signature change), the failure ADR-073 exists to prevent.

## Decision

**Ship three more first-party fakes**, extending ADR-073 to the surfaces a
concrete consumer now uses:

-   `FakeCompletionService` — the six `CompletionResponse`-returning methods
    (`complete`, `completeFactual`, `completeCreative` and their
    `*ForConfiguration` twins from [ADR-077](https://docs.typo3.org/permalink/netresearch/nr-llm:adr-077@0.35)) draw from a FIFO
    `$responses` queue; `completeJson*` and `completeMarkdown*` return
    canned properties. Every call is recorded.
-   `FakeVisionService` — the four string-or-array methods return the canned
    string echoing the caller's arity (single image → string, batch → one per
    input); `analyzeImageFull` returns a canned `VisionResponse`.
-   `FakeBudgetService` — `check()` returns a canned `BudgetCheckResult`
    (allowing by default) and records every call.

Each is a plain `final class` (not `readonly` — the canned-value and
call-recording properties are set by tests) implementing the real interface,
so PHPStan level 10 keeps the double in lock-step with the production
contract. Each carries a one-shot `$throwable` to exercise a consumer's
error path.

Beyond ADR-073's named trio, this includes **Budget** (not a
`Service\Feature\` interface, but the one whose signature drift concretely
broke consumers) and omits **translation** (no consumer needs it yet — the
same demand-pull rule ADR-073 set).

## Consequences

-   Consumers type-hint their unit tests against a maintained fake instead of a
    hand-rolled double; a future signature change fails the build *here* rather
    than silently in every consumer.
-   The three interfaces each gain a second implementor (the fake). A future
    signature change now has a production + fake blast radius — intended: the
    fake failing PHPStan is the guardrail.
-   Purely additive and DI-neutral: `Classes/Testing/*` is already excluded
    from container autoconfiguration (`Configuration/Services.yaml`) and
    covered by the production PSR-4 autoload, so the public-service count
    ([ADR-028](https://docs.typo3.org/permalink/netresearch/nr-llm:adr-028@0.35)) is unchanged and consumers get the doubles
    without nr_llm dev dependencies.
-   The `Testing\` surface (property and method names) is a supported public
    API, as ADR-073 established: renames are breaking changes and belong in
    release notes.