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_erasebackword.vim b/src/testdir/test_erasebackword.vim
index 9522ec2..b917e66 100644
--- a/src/testdir/test_erasebackword.vim
+++ b/src/testdir/test_erasebackword.vim
@@ -1,3 +1,4 @@
+" Test for i_CTRL-W
 
 func Test_erasebackword()
   enew
@@ -17,3 +18,5 @@
 
   enew!
 endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab