RST305 test case

Author: peterjc

tests/RST305/subsitution.py

@@ -0,0 +1,19 @@
+"""Print 'Hello world' to the terminal.
+
+Here's where the |foo| substitution is used - it is defined
+below.
+
+.. |foo| replace:: Here's where it's defined.
+
+So far so good, but what if the definition is not in the same
+docstring fragment - it could be in an included footer?
+
+Here the |bar| substituion definition is missing, so this
+docstring in isolation should fail validation::
+
+    $ flake8 --select RST RST305/substitution.py
+    RST305/subsitution.py:12:1: RST305 Undefined substitution referenced: "bar"
+
+"""
+
+print("Hello world")