feat: add tool respond helpers, test harness

src/tools/respond.ts

@@ -0,0 +1,13 @@
+import type { CallToolResult } from '@modelcontextprotocol/sdk/types.js'
+
+export const ok = (payload: unknown): CallToolResult => ({
+    content: [{ type: 'text', text: JSON.stringify(payload, null, 2) }]
+})
+
+export const fail = (message: string): CallToolResult => ({
+    content: [{ type: 'text', text: message }],
+    isError: true
+})
+
+export const errorMessage = (error: unknown): string =>
+    error instanceof Error ? error.message : String(error)

test/unit/helpers.ts

@@ -0,0 +1,46 @@
+import { Client } from '@modelcontextprotocol/sdk/client/index.js'
+import { InMemoryTransport } from '@modelcontextprotocol/sdk/inMemory.js'
+import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
+import { type Mock, vi } from 'vitest'
+import type { Manager } from '../../src/db/manager.js'
+
+export type ToolResponse = {
+    isError: boolean
+    text: string
+    json: () => unknown
+}
+
+// Manager whose methods are also vitest mocks — no `as unknown as Manager` casts in tests.
+export type FakeManager = Manager & {
+    get: Mock
+    invalidate: Mock
+    disposeAll: Mock
+}
+
+export const fakeManager = (): FakeManager => ({
+    get: vi.fn(),
+    invalidate: vi.fn(async () => {}),
+    disposeAll: vi.fn(async () => {})
+})
+
+export const connectClient = async (server: McpServer): Promise<Client> => {
+    const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair()
+    const client = new Client({ name: 'test-client', version: '0.0.0' })
+    await Promise.all([client.connect(clientTransport), server.connect(serverTransport)])
+    return client
+}
+
+export const callTool = async (
+    client: Client,
+    name: string,
+    args: Record<string, unknown> = {}
+): Promise<ToolResponse> => {
+    const result = await client.callTool({ name, arguments: args })
+    const content = result.content as Array<{ type: string; text: string }>
+    const text = content?.[0]?.text ?? ''
+    return {
+        isError: Boolean(result.isError),
+        text,
+        json: () => JSON.parse(text)
+    }
+}