test: enhance test-common.js

* refactor test-common.js so that global leak detection does not need to
  be disabled
* add test for common.fail()

PR-URL: #11433
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

test/parallel/test-common.js

@@ -2,14 +2,25 @@
 const common = require('../common');
 const assert = require('assert');
 
-common.globalCheck = false;
+
+// test for leaked global detection
 global.gc = 42;  // Not a valid global unless --expose_gc is set.
 assert.deepStrictEqual(common.leakedGlobals(), ['gc']);
+delete global.gc;
+
 
+// common.mustCall() tests
 assert.throws(function() {
   common.mustCall(function() {}, 'foo');
 }, /^TypeError: Invalid expected value: foo$/);
 
 assert.throws(function() {
   common.mustCall(function() {}, /foo/);
 }, /^TypeError: Invalid expected value: \/foo\/$/);
+
+
+// common.fail() tests
+assert.throws(
+  () => { common.fail('fhqwhgads'); },
+  /^AssertionError: fhqwhgads$/
+);