diff --git a/Contributing.md b/Contributing.md
index 96d9977..7bc7c59 100644
--- a/Contributing.md
+++ b/Contributing.md
@@ -100,12 +100,18 @@ Now we can generate the reference images:
 ```
 gulp makeref
 ```
-You can then run the test suite from the PDF.js root folder:
+You can then run the test suite from the PDF.js root folder after unstashing any changes:
 
 ```
 gulp test
 ```
 
+If you wish to add a reference test for your patch, you can place the file (`foo.pdf` in this example) in the `test/pdfs` directory and run the following script from the PDF.js root folder to add it to the suite:
+
+```
+node test/add_test.js test/pdfs/foo.pdf
+```
+
 **Running unit tests separately**
 
 Unit tests are run when `gulp test` is run, but they can also be run separately two different ways: