patch 9.0.1257: code style is not check in test scripts

Problem:    Code style is not check in test scripts.
Solution:   Add basic code style check for test files.
diff --git a/src/testdir/test_virtualedit.vim b/src/testdir/test_virtualedit.vim
index 7ad54db..71cea42 100644
--- a/src/testdir/test_virtualedit.vim
+++ b/src/testdir/test_virtualedit.vim
@@ -585,14 +585,14 @@
   set virtualedit&
 endfunc
 
-" this was replacing the NUL at the end of the line 
+" this was replacing the NUL at the end of the line
 func Test_virtualedit_replace_after_tab()
   new
   s/\v/	0
   set ve=all
   let @" = ''
   sil! norm vPvr0
-  
+
   call assert_equal("\t0", getline(1))
   set ve&
   bwipe!