Get the TSLint tempname test running on Windows

test/handler/test_tslint_handler.vader

@@ -12,6 +12,9 @@ After:
   Restore
 
   unlet! b:ale_typescript_tslint_ignore_empty_files
+  unlet! b:relative_to_root
+  unlet! b:tempname_suffix
+  unlet! b:relative_tempname
 
   call ale#test#RestoreDirectory()
   call ale#linter#Reset()
@@ -282,9 +285,12 @@ Execute(The tslint handler should not report no-implicit-dependencies errors):
   \ }])])
 
 Execute(The tslint handler should set filename keys for temporary files):
-  if !has('win32')
   " The temporay filename below is hacked into being a relative path so we can
   " test that we resolve the temporary filename first.
+  let b:relative_to_root = substitute(expand('%:p'), '\v[^/\\]*([/\\])[^/\\]*', has('win32') ? '..\' : '../', 'g')
+  let b:tempname_suffix = substitute(tempname(), '^\v([A-Z]:)?[/\\]', '', '')
+  let b:relative_tempname = b:relative_to_root . b:tempname_suffix
+
   AssertEqual
   \ [
   \   {'lnum': 47, 'col': 1, 'code': 'curly', 'end_lnum': 47, 'type': 'E', 'end_col': 26, 'text': 'if statements must be braced'},
@@ -297,7 +303,7 @@ Execute(The tslint handler should set filename keys for temporary files):
   \       'position':1383,
   \     },
   \     'failure': 'if statements must be braced',
-    \     'name': substitute(substitute(substitute(expand('%:p'), '[^/\\]', '', 'g'), '.', '../', 'g') . tempname(), '\([A-Z]:\\\)[A-Z]:', '\1', ''),
+  \     'name': b:relative_tempname,
   \     'ruleName': 'curly',
   \     'ruleSeverity':'ERROR',
   \     'startPosition': {
@@ -307,4 +313,3 @@ Execute(The tslint handler should set filename keys for temporary files):
   \     }
   \   },
   \ ])])
-  endif