lemon_platform_test

lemon_platform_test is Lemon's contract-test kit. Its ExUnit case templates run behaviour-compliance suites against an extension implementation before it reaches a user. The kit covers LemonChannels.Plugin (PluginCase), LemonCore.Store.Backend (BackendCase), LemonMemory.Provider (ProviderCase), and the typed bus payloads of LemonCore.Events (EventsCase, for extensions that publish their own events; see Typed Bus Events). It also ships two test helpers: LemonPlatformTest.EventsFixtures (builders for valid typed payloads) and LemonPlatformTest.FakeLLM (a scripted LLM stream function for LemonAgent loops with no network or API key).

Gateway engines are deliberately not an extension contract. The Gateway engine behaviour, registry, Echo reference implementation, and EngineCase were removed when Gateway moved to its configured singleton executor. Do not use this package to add a top-level executor or vendor CLI to Gateway.

Choose the correct extension point

Need	Extension point
Integrate another model/API	LemonAi.Provider
Add agent capability	a CodingAgent tool
Run delegated work	a native in-process subagent (CodingAgent.Session via the task tool)
Add a messaging channel	LemonChannels.Plugin
Add a store or memory backend	LemonCore.Store.Backend or LemonMemory.Provider

Delegated tasks run natively in-process: a subagent is a child CodingAgent.Session coordinated by CodingAgent.Coordinator, and there are no vendor CLI runners (Claude Code, Codex, Kimi, OpenCode, and Pi were removed). Top-level engine: "lemon" is fixed compatibility provenance, while a delegated task retains its own task identity. Neither is a direct Gateway executor.

Each case template's moduledoc is the reference guide for its behaviour: the use line, a minimal implementation, every suite option, and optional callbacks. The suites test contracts rather than implementation internals and avoid network calls, message delivery, and real task runs unless an explicit probe opts in.

Using the kit

defmodule MyApp.RedisBackendComplianceTest do
  use LemonPlatformTest.BackendCase,
    async: true,
    backend: MyApp.RedisBackend,
    backend_opts: [url: "redis://localhost:6379/15"]
end

Each case needs exactly one platform app, and all are optional: true: BackendCase and EventsCase need lemon_core, ProviderCase needs lemon_memory, FakeLLM needs lemon_ai and lemon_agent, and PluginCase needs lemon_channels, which is not published to Hex, so outside this repository it requires a path dependency on a Lemon checkout. A missing dependency raises at compile time naming the package to add. Package details live in apps/lemon_platform_test/README.md.

test/compliance/ in this repo runs the kit against the platform's own implementations: the ETS, JSONL and SQLite store backends, the Discord, Email and Telegram channel adapters, the local memory provider, and the core event registry.

scripts/test path apps/lemon_platform_test/test --cover