test: increase coverage for path.parse

Backport-PR-URL: https://github.com/nodejs/node/pull/14787
PR-URL: https://github.com/nodejs/node/pull/14438
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>

test/parallel/test-path-parse-format.js

@@ -11,6 +11,8 @@ const winPaths = [
   'file',
   '.\\file',
   'C:\\',
+  'C:',
+  '\\',
   '',
 
   // unc
@@ -21,7 +23,9 @@ const winPaths = [
 ];
 
 const winSpecialCaseParseTests = [
-  ['/foo/bar', {root: '/'}]
+  ['/foo/bar', { root: '/' }],
+  ['C:', { root: 'C:', dir: 'C:', base: '' }],
+  ['C:\\', { root: 'C:\\', dir: 'C:\\', base: '' }]
 ];
 
 const winSpecialCaseFormatTests = [