diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 0d53a75..dd71745 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -384,6 +384,12 @@
   let s:tests = filter(s:tests, 'v:val =~ argv(1)')
 endif
 
+" If the environment variable $TEST_FILTER is set then filter the function
+" names against it.
+if $TEST_FILTER != ''
+  let s:tests = filter(s:tests, 'v:val =~ $TEST_FILTER')
+endif
+
 " Execute the tests in alphabetical order.
 for s:test in sort(s:tests)
   " Silence, please!
diff --git a/src/testdir/summarize.vim b/src/testdir/summarize.vim
index 5bbf0b3..9cf3f69 100644
--- a/src/testdir/summarize.vim
+++ b/src/testdir/summarize.vim
@@ -8,7 +8,7 @@
       let g:failed += a:match+0
     elseif a:type ==# 'skipped'
       let g:skipped += 1
-      call extend(g:skipped_output, ["\t".a:match])
+      call extend(g:skipped_output, ["\t" .. a:match])
     endif
   endfunc
 
@@ -19,6 +19,10 @@
   let g:failed_output = []
   let output = [""]
 
+  if $TEST_FILTER != ''
+    call extend(g:skipped_output, ["\tAll tests not matching $TEST_FILTER: '" .. $TEST_FILTER .. "'"])
+  endif
+
   try
     " This uses the :s command to just fetch and process the output of the
     " tests, it doesn't actually replace anything.