fix: support node20

Author: OrKoN

.github/workflows/run-tests.yml

@@ -20,6 +20,7 @@ jobs:
           - windows-latest
           - macos-latest
         node:
+          - 20
           - 22
           - 24
     steps:
@@ -32,17 +33,26 @@ jobs:
         uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5.0.0
         with:
           cache: npm
-          node-version: ${{ matrix.node }}
+          node-version: 22
 
       - name: Install dependencies
         run: npm ci
 
+      - name: Build
+        run: npm run build
+
+      - name: Set up Node.js
+        uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5.0.0
+        with:
+          cache: npm
+          node-version: ${{ matrix.node }}
+
       - name: Disable AppArmor
         if: ${{ matrix.os == 'ubuntu-latest' }}
         run: echo 0 | sudo tee /proc/sys/kernel/apparmor_restrict_unprivileged_userns
 
       - name: Run tests
-        run: npm run test
+        run: npm run test:no-build
 
   # Gating job for branch protection.
   test-success:

README.md

@@ -26,7 +26,7 @@ MCP clients.
 
 ## Requirements
 
-- [Node.js 22](https://nodejs.org/) or newer.
+- [Node.js 20](https://nodejs.org/) or newer.
 - [Chrome](https://www.google.com/chrome/) current stable version or newer.
 - [npm](https://www.npmjs.com/).
 

package.json

@@ -15,7 +15,8 @@
     "generate-docs": "npm run build && node --experimental-strip-types scripts/generate-docs.ts",
     "start": "npm run build && node build/src/index.js",
     "start-debug": "DEBUG=mcp:* DEBUG_COLORS=false npm run build && node build/src/index.js",
-    "test": "npm run build && node --require ./build/tests/setup.js --test-reporter spec --test-force-exit --test 'build/tests/**/*.test.js'",
+    "test:no-build": "node --require ./build/tests/setup.js --test-reporter spec --test-force-exit --test 'build/tests'",
+    "test": "npm run build && npm run test:no-build",
     "test:only": "npm run build && node --require ./build/tests/setup.js --test-reporter spec --test-force-exit --test --test-only 'build/tests/**/*.test.js'",
     "test:only:no-build": "node --require ./build/tests/setup.js --test-reporter spec --test-force-exit --test --test-only 'build/tests/**/*.test.js'",
     "test:update-snapshots": "npm run build && node --require ./build/tests/setup.js --test-force-exit --test --test-update-snapshots 'build/tests/**/*.test.js'",

src/index.ts

@@ -5,6 +5,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import './polyfill.js';
+
 import {McpServer} from '@modelcontextprotocol/sdk/server/mcp.js';
 import {StdioServerTransport} from '@modelcontextprotocol/sdk/server/stdio.js';
 import {

src/polyfill.ts

@@ -0,0 +1,19 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// For Node 20.
+if (!Promise.withResolvers) {
+  Promise.withResolvers = function <T>() {
+    let resolve, reject;
+    const promise = new Promise<T>((_resolve, _reject) => {
+      resolve = _resolve;
+      reject = _reject;
+    });
+    return {promise, resolve, reject} as unknown as ReturnType<
+      typeof Promise.withResolvers<T>
+    >;
+  };
+}

tests/setup.ts

@@ -5,6 +5,13 @@
  */
 import {it} from 'node:test';
 
+if (!it.snapshot) {
+  it.snapshot = {
+    setResolveSnapshotPath: () => {},
+    setDefaultSnapshotSerializers: () => {},
+  };
+}
+
 // This is run by Node when we execute the tests via the --require flag.
 it.snapshot.setResolveSnapshotPath(testPath => {
   // By default the snapshots go into the build directory, but we want them

tests/tools/performance.test.ts

@@ -161,7 +161,7 @@ describe('performance', () => {
           context,
         );
 
-        t.assert.snapshot(response.responseLines.join('\n'));
+        t.assert.snapshot?.(response.responseLines.join('\n'));
       });
     });
 

tests/trace-processing/parse.test.ts

@@ -26,6 +26,6 @@ describe('Trace parsing', async () => {
     assert.ok(result?.insights);
 
     const output = getTraceSummary(result);
-    t.assert.snapshot(output);
+    t.assert.snapshot?.(output);
   });
 });

tests/utils.ts

@@ -3,7 +3,7 @@
  * Copyright 2025 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-
+import '../src/polyfill.js';
 import puppeteer, {Browser} from 'puppeteer';
 import {HTTPRequest, HTTPResponse} from 'puppeteer-core';
 import {McpResponse} from '../src/McpResponse.js';