diff --git a/pecan/testing.py b/pecan/testing.py
index b690ff2..ee2896e 100644
--- a/pecan/testing.py
+++ b/pecan/testing.py
@@ -2,13 +2,15 @@ from pecan import load_app
 from webtest import TestApp
 
 
-def load_test_app(config):
+def load_test_app(config=None):
     """
     Used for functional tests where you need to test your
     literal application and its integration with the framework.
 
-    :param config: Can be a dictionary containing configuration, or a string
-                   which represents a (relative) configuration filename.
+    :param config: Can be a dictionary containing configuration, a string which
+                    represents a (relative) configuration filename or ``None``
+                    which will fallback to get the ``PECAN_CONFIG`` env
+                    variable.
 
     returns a pecan.Pecan WSGI application wrapped in a webtest.TestApp
     instance.
@@ -21,5 +23,13 @@ def load_test_app(config):
 
         resp = app.post('/path/to/some/resource', params={'param': 'value'})
         assert resp.status_int == 302
+
+    Alternatively you could call ``load_test_app`` with no parameters if the
+    environment variable is set ::
+
+        app = load_test_app()
+
+        resp = app.get('/path/to/some/resource').status_int
+        assert resp.status_int == 200
     """
     return TestApp(load_app(config))