patch 7.4.1097
Problem:    Looking up the alloc ID for tests fails.
Solution:   Fix the line computation.  Use assert_fails() for unlet test.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 72b21d5..fd64c98 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -48,14 +48,16 @@
 " Support function: get the alloc ID by name.
 function GetAllocId(name)
   exe 'split ' . s:srcdir . '/alloc.h'
-  /typedef enum/
-  let top = getline('.')
+  let top = search('typedef enum')
+  if top == 0
+    call add(v:errors, 'typedef not found in alloc.h')
+  endif
   let lnum = search('aid_' . a:name . ',')
   if lnum == 0
     call add(v:errors, 'Alloc ID ' . a:name . ' not defined')
   endif
   close
-  return lnum - top
+  return lnum - top - 1
 endfunc