chore: extract skipTest into its own harness module (#56)

Move skipTest from features.js into a dedicated skip-test.js file,
matching the pattern of other harness utilities (assert, must-call, gc).
Add a harness test to verify the global exists.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Chengzhong Wu <cwu631@bloomberg.net>

Author: 3 people

implementors/node/features.js

@@ -7,7 +7,3 @@ globalThis.experimentalFeatures = {
   setPrototype: true,
   postFinalizer: true,
 };
-
-globalThis.skipTest = () => {
-  process.exit(0);
-};

implementors/node/skip-test.js

@@ -0,0 +1,3 @@
+globalThis.skipTest = () => {
+  process.exit(0);
+};

implementors/node/tests.ts

@@ -40,6 +40,12 @@ const MUST_CALL_MODULE_PATH = path.join(
   "node",
   "must-call.js"
 );
+const SKIP_TEST_MODULE_PATH = path.join(
+  ROOT_PATH,
+  "implementors",
+  "node",
+  "skip-test.js"
+);
 const NAPI_VERSION_MODULE_PATH = path.join(
   ROOT_PATH,
   "implementors",
@@ -87,6 +93,8 @@ export function runFileInSubprocess(
         "--import",
         "file://" + MUST_CALL_MODULE_PATH,
         "--import",
+        "file://" + SKIP_TEST_MODULE_PATH,
+        "--import",
         "file://" + NAPI_VERSION_MODULE_PATH,
         filePath,
       ],

tests/harness/skip-test.js

@@ -0,0 +1,6 @@
+'use strict';
+
+// skipTest is a function
+if (typeof skipTest !== 'function') {
+  throw new Error('Expected a global skipTest function');
+}