patch 8.2.1432: various inconsistencies in test files

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)
diff --git a/src/testdir/test_comparators.vim b/src/testdir/test_comparators.vim
index 87be006..69f255f 100644
--- a/src/testdir/test_comparators.vim
+++ b/src/testdir/test_comparators.vim
@@ -1,3 +1,5 @@
+" Test for comparators
+
 function Test_Comparators()
   try
     let oldisident=&isident
@@ -7,3 +9,5 @@
     let &isident=oldisident
   endtry
 endfunction
+
+" vim: shiftwidth=2 sts=2 expandtab