diff --git a/src/doc/trpl/testing.md b/src/doc/trpl/testing.md
index b278ea0127686..c6aeb86f7d32a 100644
--- a/src/doc/trpl/testing.md
+++ b/src/doc/trpl/testing.md
@@ -504,3 +504,6 @@ you add more examples.
 
 We haven’t covered all of the details with writing documentation tests. For more,
 please see the [Documentation chapter](documentation.html)
+
+One final note: Tests *cannot* be run on a binary file. To see more on file arrangement see the [Crates and Modules](crates-and-modules.html) section.
+