feat: enforce ECMAScript-only globals in test files via ESLint (#30)

* Enforce ECMAScript-only globals in test files via ESLint

Add an allowlist-based ESLint config using globals.es2025 plus the CTS
harness globals (assert, loadAddon, mustCall, mustNotCall, gcUntil).
Any runtime-specific API (setTimeout, process, Buffer, etc.) now triggers
a no-undef error in tests/**/*.js files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Add experimentalFeatures global and ban globalThis/global access in tests

- Add experimentalFeatures to the allowed CTS harness globals
- Add no-restricted-syntax rule to flag globalThis.* and global.* access,
  ensuring tests use CTS harness globals (e.g. gcUntil) instead

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: kraenhansen

eslint.config.js

@@ -1,17 +1,33 @@
 import { defineConfig, globalIgnores } from "eslint/config";
+import globals from "globals";
 
 export default defineConfig([
   globalIgnores(["node"]),
   {
     files: ["tests/**/*.js"],
+    languageOptions: {
+      // Only allow ECMAScript built-ins and CTS harness globals.
+      // This causes no-undef to flag any runtime-specific API (setTimeout, process, Buffer, etc.).
+      globals: {
+        ...globals.es2025,
+        // CTS harness globals
+        assert: "readonly",
+        loadAddon: "readonly",
+        mustCall: "readonly",
+        mustNotCall: "readonly",
+        gcUntil: "readonly",
+        experimentalFeatures: "readonly",
+      },
+    },
     rules: {
-      // Test files are expected to be self-contained
+      "no-undef": "error",
       "no-restricted-imports": ["error", {
         patterns: ["*"],
       }],
-      "no-restricted-globals": ["error",
-        { name: "require", message: "Test files are expected to be self-contained" }
-      ]
+      "no-restricted-syntax": ["error",
+        { selector: "MemberExpression[object.name='globalThis']", message: "Avoid globalThis access in test files — use CTS harness globals instead" },
+        { selector: "MemberExpression[object.name='global']", message: "Avoid global access in test files — use CTS harness globals instead" }
+      ],
     },
   },
 ]);

package-lock.json

@@ -13,6 +13,7 @@
   "devDependencies": {
     "@types/node": "^24.10.1",
     "eslint": "^9.39.1",
+    "globals": "^17.4.0",
     "node-api-headers": "^1.7.0"
   },
   "dependencies": {