models: add synthetic provider

src/models/synthetic.test.ts

@@ -0,0 +1,62 @@
+import { describe, it, expect } from 'vitest';
+import { SyntheticClient } from './synthetic.js';
+import type { ChatRequest } from './types.js';
+
+function makeRequest(text: string): ChatRequest {
+  return {
+    messages: [{ role: 'user', content: text }],
+  };
+}
+
+describe('SyntheticClient', () => {
+  it('echoes the last user message by default', async () => {
+    const client = new SyntheticClient({ model: 'echo' });
+    const res = await client.chat(makeRequest('hello'));
+    expect(res.content).toBe('hello');
+    expect(res.stopReason).toBe('end_turn');
+    expect(res.toolCalls).toBeUndefined();
+    expect(res.usage.inputTokens).toBeGreaterThan(0);
+    expect(res.usage.outputTokens).toBeGreaterThan(0);
+  });
+
+  it('supports fixed responses via model=fixed:<text>', async () => {
+    const client = new SyntheticClient({ model: 'fixed:ok' });
+    const res = await client.chat(makeRequest('ignored'));
+    expect(res.content).toBe('ok');
+    expect(res.stopReason).toBe('end_turn');
+  });
+
+  it('supports tool calls via @tool directive', async () => {
+    const client = new SyntheticClient({ model: 'echo' });
+    const res = await client.chat(makeRequest('@tool memory.read {"namespace":"global"}'));
+    expect(res.stopReason).toBe('tool_use');
+    expect(res.content).toBe('');
+    expect(res.toolCalls?.length).toBe(1);
+    expect(res.toolCalls?.[0]?.name).toBe('memory.read');
+    expect(res.toolCalls?.[0]?.args).toEqual({ namespace: 'global' });
+  });
+
+  it('streams content + done', async () => {
+    const client = new SyntheticClient({ model: 'fixed:stream-me' });
+    const events: string[] = [];
+    for await (const ev of client.chatStream!(makeRequest('x'))) {
+      events.push(ev.type);
+    }
+    expect(events).toEqual(['content', 'done']);
+  });
+
+  it('streams tool_use + done for @tool directives', async () => {
+    const client = new SyntheticClient({ model: 'echo' });
+    const types: string[] = [];
+    const toolNames: string[] = [];
+    for await (const ev of client.chatStream!(makeRequest('@tool file.read {"path":"README.md"}'))) {
+      types.push(ev.type);
+      if (ev.type === 'tool_use' && ev.toolCall) {
+        toolNames.push(ev.toolCall.name);
+      }
+    }
+    expect(types).toEqual(['tool_use', 'done']);
+    expect(toolNames).toEqual(['file.read']);
+  });
+});
+