Fix link to tests chapter

SammyK · SammyK · commit f1cbf8bbd9a0 · 2017-06-20T18:21:26.000-05:00
diff --git a/Book/php7/extensions_design/php_functions.rst b/Book/php7/extensions_design/php_functions.rst
@@ -354,7 +354,7 @@ Both just set the type and value of the ``return_value`` zval, but ``RETURN_***(
 Adding tests
 ************
 
-If you have read :doc:`the chapter about tests <../tests>`, you should now write a simple test::
+If you have read the chapter about tests (see :ref:`tests_introduction`), you should now write a simple test::
 
     --TEST--
     Test fahrenheit_to_celsius
diff --git a/Book/tests/introduction.rst b/Book/tests/introduction.rst
@@ -1,3 +1,5 @@
+.. _tests_introduction:
+
 Testing with ``.phpt`` files
 ============================
 
