TDD Green Phase - Make Tests Pass Quickly

TDD Green Phase - Make Tests Pass Quickly (graphdo-ts)

Write the minimal code necessary to make failing vitest tests pass. Resist the urge to write more than required.

Always read AGENTS.md before implementing — it defines the exact patterns all code in this project must follow.

Core Principles

• Just enough code — implement only what's needed to make the test pass
• Follow existing patterns — look at src/graph/mail.ts or src/graph/todo.ts as models for Graph operations; look at src/tools/mail.ts or src/tools/todo.ts for tool registration patterns
• Minimal implementation — start simple, generalise only when forced by additional tests
• Don't modify tests — the test defines the contract; the implementation must conform to it

The graphdo-ts Implementation Patterns

Adding a Graph Operation (src/graph/)

Look at src/graph/mail.ts as the model:

import type { GraphClient } from "./client.js";
import type { SomeType } from "./types.js";

export async function getSomething(client: GraphClient, id: string): Promise<SomeType> {
  const result = await client.request<SomeType>("GET", `/me/some/resource/${id}`);
  return result;
}

export async function createSomething(
  client: GraphClient,
  data: { field: string },
): Promise<SomeType> {
  return client.request<SomeType>("POST", "/me/some/resource", data);
}

Adding a Tool Registration (src/tools/)

Look at src/tools/mail.ts as the model:

import { z } from "zod";
import type { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { GraphClient } from "../graph/client.js";
import { AuthenticationRequiredError } from "../auth.js";
import { logger } from "../logger.js";
import type { ServerConfig } from "../index.js";
import { getSomething } from "../graph/some.js";

export function registerSomeTools(server: McpServer, config: ServerConfig): void {
  server.registerTool(
    "some_tool",
    {
      description: "Does something with the Graph API",
      inputSchema: { id: z.string().min(1).describe("Resource ID") },
      annotations: { readOnlyHint: true },
    },
    async ({ id }) => {
      try {
        const token = await config.authenticator.token();
        const client = new GraphClient(config.graphBaseUrl, token);
        const result = await getSomething(client, id);
        return { content: [{ type: "text", text: JSON.stringify(result, null, 2) }] };
      } catch (error: unknown) {
        const message = error instanceof Error ? error.message : String(error);
        logger.error("some_tool failed", { error: message });
        return { isError: true, content: [{ type: "text", text: `Error: ${message}` }] };
      }
    },
  );
}