diff --git a/runtime/syntax/testdir/README.txt b/runtime/syntax/testdir/README.txt
index d8ac066..e4f3945 100644
--- a/runtime/syntax/testdir/README.txt
+++ b/runtime/syntax/testdir/README.txt
@@ -117,7 +117,7 @@
 
 If you make changes to the syntax plugin, you should add code to the input
 file to see the effect of these changes.  So that the effect of the changes
-are covered by the test.  You can follow these steps:
+is covered by the test.  You can follow these steps:
 
 1. Edit the syntax plugin somewhere in your personal setup.  Use a file
    somewhere to try out the changes.
@@ -133,19 +133,19 @@
    Fix the syntax plugin until the result is good.
 2. Edit the input file for your language to add the items you have improved.
    (TODO: how to add another screendump?).
-   Run the tests and you should get failures.  Like with the previous step,
-   carefully check that the new screendumps in the "failed" directory are
-   good.  Update the syntax plugin and the input file until the highlighting
-   is good and you can see the effect of the syntax plugin improvements.  Then
-   move the screendumps from the "failed" to the "dumps" directory.  Now "make
-   test" should succeed.
+   Run the tests and you should get failures.  (You may opt for faster failure
+   by assigning a small number, e.g. "1", to a VIM_SYNTAX_TEST_WAIT_TIME
+   environment variable and gambling away an "uncertain" possibility of
+   success.)  Like with the previous step, carefully check that the new
+   screendumps in the "failed" directory are good.  Update the syntax plugin
+   and the input file until the highlighting is good and you can see the
+   effect of the syntax plugin improvements.  Then move the screendumps from
+   the "failed" to the "dumps" directory.  Now "make test" should succeed.
 3. Prepare a pull request with the modified files:
 	- syntax plugin:    syntax/{name}.vim
 	- Vim setup file:   syntax/testdir/input/setup/{name}.vim (if any)
 	- test input file:  syntax/testdir/input/{name}.{ext}
-	- test dump files:  syntax/testdir/dumps/{name}_00.dump
-			    syntax/testdir/dumps/{name}_01.dump (if any)
-			    ...
+	- test dump files:  syntax/testdir/dumps/{name}_*.dump
 
 As an extra check you can temporarily put back the old syntax plugin and
 verify that the tests fail.  Then you know your changes are covered by the
diff --git a/runtime/syntax/testdir/runtest.vim b/runtime/syntax/testdir/runtest.vim
index 19a5e89..4152702 100644
--- a/runtime/syntax/testdir/runtest.vim
+++ b/runtime/syntax/testdir/runtest.vim
@@ -383,7 +383,11 @@
     enddef
   END
   let MAX_FAILED_COUNT = 5
-  lockvar MAX_FAILED_COUNT XTESTSCRIPT
+  let DUMP_OPTS = exists("$VIM_SYNTAX_TEST_WAIT_TIME") &&
+	  \ !empty($VIM_SYNTAX_TEST_WAIT_TIME)
+      \ ? {'wait': max([1, str2nr($VIM_SYNTAX_TEST_WAIT_TIME)])}
+      \ : {}
+  lockvar DUMP_OPTS MAX_FAILED_COUNT XTESTSCRIPT
   let ok_count = 0
   let failed_tests = []
   let skipped_count = 0
@@ -398,8 +402,8 @@
 	\ ->join('\|')
     \ : ''
 
-  " Treat "\.self-testing$" as a string NOT as a regexp.
-  if filter ==# '\.self-testing$'
+  " Treat "^self-testing" as a string NOT as a regexp.
+  if filter ==# '^self-testing'
     let dirpath = 'input/selftestdir/'
     let fnames = readdir(dirpath, {fname -> fname !~ '^README\.txt$'})
   else
@@ -472,7 +476,7 @@
       let ruler = s:TermWaitAndPollRuler(buf, in_name_and_out_name)
       call ch_log('First screendump for ' .. in_name_and_out_name)
       " Make a screendump at the start of the file: failed/root_00.dump
-      let fail = VerifyScreenDump(buf, root_00, {})
+      let fail = VerifyScreenDump(buf, root_00, DUMP_OPTS)
 
       " Accommodate the next code block to "buf"'s contingency for self
       " wipe-out.
@@ -492,7 +496,7 @@
 	      \ in_name_and_out_name)
 	  call ch_log('Next screendump for ' .. in_name_and_out_name)
 	  " Make a screendump of every 18 lines of the file: failed/root_NN.dump
-	  let fail += VerifyScreenDump(buf, root_next, {})
+	  let fail += VerifyScreenDump(buf, root_next, DUMP_OPTS)
 	endwhile
 	call StopVimInTerminal(buf)
       finally