diff --git a/HowToWriteTests.md b/HowToWriteTests.md
index 8d5e491..c8d0470 100644
--- a/HowToWriteTests.md
+++ b/HowToWriteTests.md
@@ -22,6 +22,8 @@ class T(unittest.TestCase):
 
 Now run it!
 
+Also read: <https://tahoe-lafs.org/trac/setuptools_trial/browser/trunk/README.txt>
+
 # code coverage
 
 Now install Ned Batchelder's "[coverage"](http://nedbatchelder.com/code/coverage/) tool and run your with code coverage, like this: