test: allow leaked global check to be skipped

This simplifies the process of running tests on different
versions of Node, which might have a different set of
global variables.

PR-URL: nodejs#27239
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/common/index.js

@@ -279,34 +279,36 @@ if (global.gc) {
   knownGlobals.push(global.gc);
 }
 
-if (process.env.NODE_TEST_KNOWN_GLOBALS) {
-  const knownFromEnv = process.env.NODE_TEST_KNOWN_GLOBALS.split(',');
-  allowGlobals(...knownFromEnv);
-}
-
 function allowGlobals(...whitelist) {
   knownGlobals = knownGlobals.concat(whitelist);
 }
 
-function leakedGlobals() {
-  const leaked = [];
+if (process.env.NODE_TEST_KNOWN_GLOBALS !== '0') {
+  if (process.env.NODE_TEST_KNOWN_GLOBALS) {
+    const knownFromEnv = process.env.NODE_TEST_KNOWN_GLOBALS.split(',');
+    allowGlobals(...knownFromEnv);
+  }
 
-  for (const val in global) {
-    if (!knownGlobals.includes(global[val])) {
-      leaked.push(val);
+  function leakedGlobals() {
+    const leaked = [];
+
+    for (const val in global) {
+      if (!knownGlobals.includes(global[val])) {
+        leaked.push(val);
+      }
     }
+
+    return leaked;
   }
 
-  return leaked;
+  process.on('exit', function() {
+    const leaked = leakedGlobals();
+    if (leaked.length > 0) {
+      assert.fail(`Unexpected global(s) found: ${leaked.join(', ')}`);
+    }
+  });
 }
 
-process.on('exit', function() {
-  const leaked = leakedGlobals();
-  if (leaked.length > 0) {
-    assert.fail(`Unexpected global(s) found: ${leaked.join(', ')}`);
-  }
-});
-
 const mustCallChecks = [];
 
 function runCallChecks(exitCode) {

test/parallel/test-common.js

@@ -35,6 +35,17 @@ const { execFile } = require('child_process');
   }));
 }
 
+// Test for disabling leaked global detection
+{
+  const p = fixtures.path('leakedGlobal.js');
+  execFile(process.execPath, [p], {
+    env: { ...process.env, NODE_TEST_KNOWN_GLOBALS: 0 }
+  }, common.mustCall((err, stdout, stderr) => {
+    assert.strictEqual(err, null);
+    assert.strictEqual(stderr.trim(), '');
+  }));
+}
+
 // common.mustCall() tests
 assert.throws(function() {
   common.mustCall(function() {}, 'foo');