diff --git a/bumblebee-status b/bumblebee-status
index e461758..29e7876 100755
--- a/bumblebee-status
+++ b/bumblebee-status
@@ -11,12 +11,12 @@ def main():
     modules = []
     for module in config.modules():
         modules.append(core.module.load(module))
+    output.modules(modules)
     output.draw('start')
     while True:
         output.clear()
         for module in modules:
             module.update()
-            output.append(module)
         output.draw('statusline')
         output.wait(config.interval())
     output.draw('stop')
diff --git a/core/output.py b/core/output.py
index 9a6b898..f10b486 100644
--- a/core/output.py
+++ b/core/output.py
@@ -4,8 +4,14 @@ import time
 
 class i3(object):
     def __init__(self):
+        self._modules = []
         self.clear()
 
+    def modules(self, modules=None):
+        if not modules:
+            return self._modules
+        self._modules = modules if isinstance(modules, list) else [ modules ]
+
     def draw(self, what):
         data = getattr(self, what)()
         if 'data' in data:
@@ -26,15 +32,15 @@ class i3(object):
     def clear(self):
         self._statusline = []
 
-    def append(self, module):
-        for widget in module.widgets():
-            self._statusline.append({
-                'full_text': widget.full_text()
-            })
-
     def statusline(self):
+        status = []
+        for module in self._modules:
+            for widget in module.widgets():
+                status.append({
+                    'full_text': widget.full_text()
+                })
         return {
-            'data': self._statusline,
+            'data': status,
             'suffix': ','
         }
 
diff --git a/doc/NOTES.md b/doc/NOTES.md
index 5ae90e5..f437dae 100644
--- a/doc/NOTES.md
+++ b/doc/NOTES.md
@@ -16,3 +16,5 @@
 
 ## Improvements
 - pango output (improve - maybe autodetect? see #531)
+- only update specific, affected modules when clicking
+- allow handlers to specify whether to update or not (e.g. scroll)
diff --git a/tests/core/test_output.py b/tests/core/test_output.py
index e32839a..c751ed9 100644
--- a/tests/core/test_output.py
+++ b/tests/core/test_output.py
@@ -1,11 +1,18 @@
-import unittest
 import json
+import unittest
 
 import core.output
+import core.module
+
+class TestModule(core.module.Module):
+    pass
 
 class i3(unittest.TestCase):
     def setUp(self):
         self.i3 = core.output.i3()
+        widget = unittest.mock.MagicMock()
+        widget.full_text.return_value = "test"
+        self.someModule = TestModule([widget, widget, widget])
 
     def tearDown(self):
         pass
@@ -18,8 +25,34 @@ class i3(unittest.TestCase):
         self.assertEqual('\n[', all_data['suffix'])
 
     def test_stop(self):
-        self.assertEqual('\n]', self.i3.stop()['suffix'])
+        self.assertEqual('\n]', self.i3.stop()['suffix'], 'wrong i3bar protocol during stop')
 
-    # TODO: mock a "draw" call
+    def test_no_modules_by_default(self):
+        self.assertEqual(0, len(self.i3.modules()), 'module list should be empty by default')
+
+    def test_register_single_module(self):
+        self.i3.modules(self.someModule)
+        self.assertEqual(1, len(self.i3.modules()), 'setting single module does not work')
+
+    def test_register_multiple_modules(self):
+        self.i3.modules([ self.someModule, self.someModule, self.someModule ])
+        self.assertEqual(3, len(self.i3.modules()), 'setting module list does not work')
+
+    def test_draw_existing_module(self):
+        self.i3.test_draw = unittest.mock.MagicMock(return_value={
+            'data': { 'test': True }, 'suffix': 'end'
+        })
+        self.i3.draw('test_draw')
+        self.i3.test_draw.assert_called_once_with()
+
+    def test_empty_status_line(self):
+        data = self.i3.statusline()
+        self.assertEqual([], data['data'], 'expected empty list of status line entries')
+        self.assertEqual(',', data['suffix'], 'expected "," as suffix')
+
+    def test_statusline(self):
+        self.i3.modules([ self.someModule, self.someModule, self.someModule ])
+        data = self.i3.statusline()
+        self.assertEqual(len(self.someModule.widgets())*3, len(data['data']), 'wrong number of widgets')
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4