[LinuxDevil]

What

Adds mockModel(script, options?) to @loushy/build-ai-agent/testing: a typed, scripted LLMProvider test double.

const model = mockModel([
  { toolCalls: [{ name: 'get_weather', args: { city: 'Paris' } }] },
  { text: 'It is 21°C in Paris.' },
]);
const agent = createAgent({ prompt: '...', provider: model, tools });
await agent.send('Weather in Paris?');
expect(model.calls).toHaveLength(2);
model.assertExhausted();

• Turns: string, { text }, { toolCalls, text? }, { error }, or (request) => turn (sync/async); optional usage, finishReason, delayMs.
• Deterministic tool-call ids (call_1, ...), calls (deep-frozen snapshots), lastCall, reset(), assertExhausted().
• Exhaustion error names the unexpected call number, shows the last message and suggests adding a turn or { onExhausted: 'repeat-last' }.
• stream() emits scripted text as chunks, then tool-call and finish chunks.
• /testing now exports a new src/testing/index.ts barrel (existing repo mocks + mockModel); package.json exports["./testing"] and the tsup entry were repointed.
• Docs: new docs/testing.md, linked from README and docs/api-overview.md.

Why

Many tests hand-roll "scripted provider" objects; competitors ship mock models for deterministic evals. This removes that boilerplate.

How verified

• npx tsc --noEmit: clean
• npm run lint: 0 errors (no new warnings from my files)
• npm run build + create-loushy-agent build: success; dist/testing/index.{js,mjs,d.ts} emitted
• npm run test:coverage: Test Files 89 passed (89), Tests 955 passed | 3 skipped
• npm run fallow: exit 0 (0 above threshold, maintainability 92.4)
• npm run docs:verify-snippets (quick-start + docs/testing.md): all snippets type-check and run (vitest-based snippets are marked no-verify since vitest is not in the temp project; the same flow is covered by src/testing/mockModel.test.ts)

Notes for reviewer

• Dogfood: DelegationTool.test.ts (4 tests + the A<->B loop test) and sandbox-wiring.test.ts converted. Net diff of those two files: 26 insertions, 104 deletions (78 lines saved). Because mockModel records a snapshot at call time, assertions no longer include the assistant message the executor pushes onto the shared array after the call (the old tests had comments about this aliasing).
• Request snapshots copy plain objects/arrays and keep functions/class instances (e.g. zod schemas in tool definitions) by reference, since those cannot be structurally cloned.

🤖 Generated with Claude Code