diff --git a/.gitignore b/.gitignore
index e43b0f988..63e98d103 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 .DS_Store
+tmp/
diff --git a/test.sh b/test.sh
index 51d16b7af..35d15ec26 100755
--- a/test.sh
+++ b/test.sh
@@ -1,10 +1,13 @@
 #!/bin/sh
 
+# create a temporary directory if it doesn't already exist
+mkdir -p tmp
+
 # cook the recipe with the old cook.rb (assuming you have set it up as described in github.com/TiddlyWiki/cooker)
-cook $PWD/test/data/tiddlywiki.com/index.html.recipe -d $PWD -o oldcooked.html
+cook $PWD/test/data/tiddlywiki.com/index.html.recipe -d $PWD -o tmp/oldcooked.html || exit 1
 
 # cook it with cook.js
-node cook.js $PWD/test/data/tiddlywiki.com/index.html.recipe > newcooked.html
+node cook.js $PWD/test/data/tiddlywiki.com/index.html.recipe > tmp/newcooked.html || exit 1
 
 # compare the two
-opendiff oldcooked.html newcooked.html
+opendiff tmp/oldcooked.html tmp/newcooked.html