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

Context 

ADR-073 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) 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) 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.