[Platform] Add Mock test provider for routing-aware, any-result-type mocks

[wachterjohannes]

Q	A
Bug fix?	no
New feature?	yes
Docs?	yes
Issues	-
License	MIT

Adds a provider-level test mock under Symfony\AI\Platform\Mock that registers like a real bridge, participates in model routing, returns scripted responses of any result type, and records call history for assertions.

Why not just Test\InMemoryPlatform?

Test\InMemoryPlatform is a platform-level fake: it replaces the whole Platform, ignores routing, has no model catalog, and returns text only — perfect for unit tests injecting a PlatformInterface directly. The new Mock provider is provider-level and complementary. Reach for it when a test must:

• go through real DI / routing (functional tests),
• coexist with real providers and prove routing picks the mock (multi-provider tests),
• return non-text results (ObjectResult, StreamResult, ToolCallResult, VectorResult),
• assert on exactly what the platform sent (recorded call history via getCalls()).

Design

MockModelClient::request() resolves a scripted ResultInterface (or wraps a string in TextResult), records the call, and threads the result through the object slot of the existing InMemoryRawResult. MockResultConverter::convert() pulls it back out and returns it verbatim — so every result type is supported with no per-type conversion code. The embedding-mock case falls out for free by scripting a VectorResult.

Usage

use Symfony\AI\Platform\Mock\Factory;
use Symfony\AI\Platform\Result\ObjectResult;

// string — every call returns a TextResult
$platform = Factory::createPlatform("Hello world");
$platform->invoke("any-model", "question")->asText(); // "Hello world"

// map keyed by model name
$platform = Factory::createPlatform(["gpt-4o" => "answer"]);

// closure — branch on payload/options
$platform = Factory::createPlatform(
    static fn ($model, $payload, $options) => isset($options["response_format"])
        ? new ObjectResult((object) ["ok" => true])
        : "plain text",
);

It lives in platform core (not under src/Bridge/, which splitsh.json excludes from the symfony/ai-platform package), so it ships with the platform exactly like Test\InMemoryPlatform.

Scope / follow-ups

• Out: ai-bundle config node (framework.ai.platform.mock) — closures cannot be expressed in YAML; most consumers register the mock in a test kernel / compiler pass. The PHP API is what unblocks them.
• Out: a mock Contract/normalizer (the mock records payloads raw) and fault injection (scripted exceptions) — easy to add later.

Verification

• vendor/bin/phpunit tests/Mock — 21 tests, 38 assertions, green.
• vendor/bin/phpstan analyse — clean.
• php-cs-fixer — clean.

[OskarStark]

Shall we name it to Mock? AFAIK this is more the Symfony naming

[wachterjohannes]

Shall we name it to Mock? AFAIK this is more the Symfony naming

Good call 👍

done — renamed Fake → Mock, have also done the same rename to the stacked PRs: #2128 and #2129