fix: use proper initialization for servers in tests

- Make test servers use ts and init them with tsx - Add test to check if
hanging server actually gets killed

Author: johnnyasantoss

src/integration-tests/process-cleanup.test.ts

@@ -3,6 +3,7 @@ import { Client } from '../client/index.js';
 import { StdioClientTransport } from '../client/stdio.js';
 import { Server } from '../server/index.js';
 import { StdioServerTransport } from '../server/stdio.js';
+import { LoggingMessageNotificationSchema } from '../types.js';
 
 describe('Process cleanup', () => {
     vi.setConfig({ testTimeout: 5000 }); // 5 second timeout
@@ -52,22 +53,58 @@ describe('Process cleanup', () => {
         });
 
         const transport = new StdioClientTransport({
-            command: process.argv0,
-            args: ['test-server.js'],
+            command: 'npm',
+            args: ['exec', 'tsx', 'test-server.ts'],
             cwd: __dirname
         });
 
+        await client.connect(transport);
+
         let onCloseWasCalled = 0;
         client.onclose = () => {
             onCloseWasCalled++;
         };
 
-        await client.connect(transport);
         await client.close();
 
         // A short delay to allow the close event to propagate
         await new Promise(resolve => setTimeout(resolve, 50));
 
         expect(onCloseWasCalled).toBe(1);
     });
+
+    it('should exit cleanly for a server that hangs', async () => {
+        const client = new Client({
+            name: 'test-client',
+            version: '1.0.0'
+        });
+
+        const transport = new StdioClientTransport({
+            command: 'npm',
+            args: ['exec', 'tsx', 'server-that-hangs.ts'],
+            cwd: __dirname
+        });
+
+        await client.connect(transport);
+        await client.setLoggingLevel('debug');
+        client.setNotificationHandler(LoggingMessageNotificationSchema, notification => {
+            console.debug('server log: ' + notification.params.data);
+        });
+        const serverPid = transport.pid!;
+
+        await client.close();
+
+        // A short delay to allow the close event to propagate
+        await new Promise(resolve => setTimeout(resolve, 50));
+
+        try {
+            process.kill(serverPid, 9);
+            throw new Error('Expected server to be dead but it is alive');
+        } catch (err: unknown) {
+            // 'ESRCH' the process doesn't exist
+            if (err && typeof err === 'object' && 'code' in err && err.code === 'ESRCH') {
+                // success
+            } else throw err;
+        }
+    });
 });

src/integration-tests/server-that-hangs.js

@@ -0,0 +1,45 @@
+import { setTimeout } from 'node:timers';
+import process from 'node:process';
+import { McpServer } from '../server/mcp.js';
+import { StdioServerTransport } from '../server/stdio.js';
+
+const transport = new StdioServerTransport();
+
+const server = new McpServer(
+    {
+        name: 'server-that-hangs',
+        title: 'Test Server that hangs',
+        version: '1.0.0'
+    },
+    {
+        capabilities: {
+            logging: {}
+        }
+    }
+);
+
+await server.connect(transport);
+
+const doNotExitImmediately = async (signal: NodeJS.Signals) => {
+    await server.sendLoggingMessage({
+        level: 'debug',
+        data: `received signal ${signal}`
+    });
+    setTimeout(() => process.exit(0), 30 * 1000);
+};
+
+transport.onclose = () => {
+    server.sendLoggingMessage({
+        level: 'debug',
+        data: 'transport: onclose called. This should never happen'
+    });
+};
+
+process.stdin.on('close', hadErr => {
+    server.sendLoggingMessage({
+        level: 'debug',
+        data: 'stdin closed. Error: ' + hadErr
+    });
+});
+process.on('SIGINT', doNotExitImmediately);
+process.on('SIGTERM', doNotExitImmediately);

src/integration-tests/server-that-hangs.ts

@@ -0,0 +1,19 @@
+import { McpServer } from '../server/mcp.js';
+import { StdioServerTransport } from '../server/stdio.js';
+
+const transport = new StdioServerTransport();
+
+const server = new McpServer({
+    name: 'test-server',
+    version: '1.0.0'
+});
+
+await server.connect(transport);
+
+const exit = async () => {
+    await server.close();
+    process.exit(0);
+};
+
+process.on('SIGINT', exit);
+process.on('SIGTERM', exit);