updating tutorial with new step 7

Author: TyDunn

docs/user-guide/rasa-tutorial.rst

@@ -226,8 +226,18 @@ The ``rasa train`` command will look for both NLU and Core data and will train a
 7. Test the model
 ^^^^^^^^^^^^^^^^^
 
-<Add explaination, runnable, and command here>
+After you train a model, you always want to check that your assistant still behaves as you expect.
+In Rasa, you use end-to-end tests defined in your ``tests/`` directory to run through
+test conversations that ensure both NLU and Core make correct predictions.
 
+.. runnable::
+
+   rasa test
+
+   echo "Finished running tests."
+
+See :ref:`evaluating-models` to find out how you can define more tests and learn about more
+ways you can evaluate your model as you improve it.
 
 8. Talk to Your Assistant
 ^^^^^^^^^^^^^^^^^^^^^^^^^