diff --git a/src/z3c/autoinclude/api.py b/src/z3c/autoinclude/api.py
index 719e5c1..8cb6ca8 100644
--- a/src/z3c/autoinclude/api.py
+++ b/src/z3c/autoinclude/api.py
@@ -14,7 +14,7 @@ def disable_dependencies():
 
 
 def enable_dependencies():
-    del os.environ[DEP_KEY]
+    os.environ.pop(DEP_KEY, None)
 
 
 def plugins_disabled():
@@ -26,7 +26,7 @@ def disable_plugins():
 
 
 def enable_plugins():
-    del os.environ[PLUGIN_KEY]
+    os.environ.pop(PLUGIN_KEY, None)
 
 
 def debug_enabled():
@@ -34,7 +34,7 @@ def debug_enabled():
 
 
 def disable_debug():
-    del os.environ[DEBUG_KEY]
+    os.environ.pop(DEBUG_KEY, None)
 
 
 def enable_debug():
diff --git a/src/z3c/autoinclude/api.txt b/src/z3c/autoinclude/api.txt
new file mode 100644
index 0000000..62cc511
--- /dev/null
+++ b/src/z3c/autoinclude/api.txt
@@ -0,0 +1,71 @@
+=============
+API functions
+=============
+
+The ``api.py`` module has some helpful functions.
+
+
+Plugins
+=======
+
+We can disable and enable autoincluding the plugins::
+
+    >>> from z3c.autoinclude import api
+    >>> api.plugins_disabled()
+    False
+    >>> api.disable_plugins()
+    >>> api.plugins_disabled()
+    True
+    >>> api.disable_plugins()  # called twice to see if this breaks
+    >>> api.plugins_disabled()
+    True
+    >>> api.enable_plugins()
+    >>> api.plugins_disabled()
+    False
+    >>> api.enable_plugins()  # called twice to see if this breaks
+    >>> api.plugins_disabled()
+    False
+
+
+Dependencies
+============
+
+We can disable and enable autoincluding the dependencies::
+
+    >>> from z3c.autoinclude import api
+    >>> api.dependencies_disabled()
+    False
+    >>> api.disable_dependencies()
+    >>> api.dependencies_disabled()
+    True
+    >>> api.disable_dependencies()  # called twice to see if this breaks
+    >>> api.dependencies_disabled()
+    True
+    >>> api.enable_dependencies()
+    >>> api.dependencies_disabled()
+    False
+    >>> api.enable_dependencies()  # called twice to see if this breaks
+    >>> api.dependencies_disabled()
+    False
+
+
+Debug
+=====
+
+We can disable and enable the debug report of autoincluded packages::
+
+    >>> from z3c.autoinclude import api
+    >>> api.debug_enabled()
+    False
+    >>> api.enable_debug()
+    >>> api.debug_enabled()
+    True
+    >>> api.enable_debug()  # called twice to see if this breaks
+    >>> api.debug_enabled()
+    True
+    >>> api.disable_debug()
+    >>> api.debug_enabled()
+    False
+    >>> api.disable_debug()  # called twice to see if this breaks
+    >>> api.debug_enabled()
+    False
diff --git a/src/z3c/autoinclude/tests/tests.py b/src/z3c/autoinclude/tests/tests.py
index ad75e38..7491f78 100644
--- a/src/z3c/autoinclude/tests/tests.py
+++ b/src/z3c/autoinclude/tests/tests.py
@@ -118,7 +118,14 @@ def test_suite():
 
     from pprint import pprint
 
-    suite = doctest.DocFileSuite(
+    simple_suite = doctest.DocFileSuite(
+        '../api.txt',
+        globs={'pprint': pprint},
+        checker=IgnoreCaseChecker(),
+        optionflags=doctest.ELLIPSIS,
+    )
+
+    advanced_suite = doctest.DocFileSuite(
         '../utils.txt',
         '../dependency.txt',
         '../plugin.txt',
@@ -129,7 +136,7 @@ def test_suite():
         optionflags=doctest.ELLIPSIS,
     )
 
-    return unittest.TestSuite((suite,))
+    return unittest.TestSuite((simple_suite, advanced_suite))
 
 
 if __name__ == '__main__':