Add end-to-end test suite (#2167)

test/e2e/fixtures/stdio-server.ts

@@ -0,0 +1,61 @@
+/**
+ * Runnable stdio MCP server fixture for the transport:stdio:* e2e tests.
+ *
+ * Spawned as a real child process by test/e2e/scenarios/stdio.ts. Registers a
+ * single `echo` tool, writes a readiness marker line to stderr once it is
+ * serving, and — when E2E_IGNORE_SIGTERM=1 — keeps running after stdin EOF and
+ * swallows SIGTERM so the client transport's shutdown escalation
+ * (stdin EOF → SIGTERM → SIGKILL) is observable.
+ */
+
+import { z } from 'zod/v4';
+
+import { McpServer } from '../../../src/server/mcp.js';
+import { StdioServerTransport } from '../../../src/server/stdio.js';
+
+const server = new McpServer({ name: 'stdio-echo-server', version: '1.0.0' });
+
+server.registerTool(
+    'echo',
+    {
+        description: 'Echoes the input text back as a text content block, including multi-line text.',
+        inputSchema: z.object({ text: z.string() })
+    },
+    ({ text }) => ({ content: [{ type: 'text', text }] })
+);
+
+// env-report tool: returns JSON array of environment variable names (sorted) that
+// reached the child process. This allows tests to verify the env safelist behavior.
+server.registerTool(
+    'env-report',
+    {
+        description: 'Returns sorted array of environment variable names present in this process.',
+        inputSchema: z.object({})
+    },
+    () => {
+        const envKeys = Object.keys(process.env).sort();
+        return { content: [{ type: 'text', text: JSON.stringify(envKeys) }] };
+    }
+);
+
+if (process.env.E2E_IGNORE_SIGTERM === '1') {
+    // Misbehaving-server mode: keep alive after stdin EOF via interval (load-bearing — without it the child exits on stdin EOF and SIGTERM never arrives) and ignore SIGTERM, so only SIGKILL can end the process.
+    setInterval(() => {}, 1_000);
+    setTimeout(() => process.exit(1), 30_000);
+    process.on('SIGTERM', () => {
+        process.stderr.write('[stdio-server] sigterm ignored\n');
+    });
+}
+
+if (process.env.E2E_GARBAGE_STDOUT === '1') {
+    // Broken-server mode: write non-JSON garbage to stdout before the server connects, simulating a broken or misconfigured server that pollutes the JSON-RPC channel.
+    process.stdout.write('GARBAGE LINE 1: not json\n');
+    process.stdout.write('GARBAGE LINE 2: {malformed json\n');
+    process.stdout.write('GARBAGE LINE 3: also not valid jsonrpc\n');
+    process.stdin.resume();
+    process.stdin.on('end', () => process.exit(0));
+    setTimeout(() => process.exit(1), 30_000);
+} else {
+    await server.connect(new StdioServerTransport());
+    process.stderr.write('[stdio-server] ready\n');
+}