diff --git a/keymapper/reader.py b/keymapper/reader.py
index a8e5cf6b..84041b5b 100644
--- a/keymapper/reader.py
+++ b/keymapper/reader.py
@@ -28,7 +28,7 @@ from keymapper.logger import logger
 from keymapper.getdevices import get_devices
 
 
-class KeycodeReader:
+class _KeycodeReader:
     """Keeps reading keycodes in the background for the UI to use.
 
     When a button was pressed, the newest keycode can be obtained from this
@@ -73,6 +73,12 @@ class KeycodeReader:
                 event = virtual_device.read_one()
                 if event is None:
                     break
+
+                logger.spam(
+                    'got code:%s value:%s',
+                    event.code + 8, event.value
+                )
+
                 if event.type == evdev.ecodes.EV_KEY and event.value == 1:
                     # value: 1 for down, 0 for up, 2 for hold.
                     # this happens to report key codes that are 8 lower
@@ -81,4 +87,4 @@ class KeycodeReader:
         return newest_keycode
 
 
-keycode_reader = KeycodeReader()
+keycode_reader = _KeycodeReader()
diff --git a/tests/testcases/injector.py b/tests/testcases/injector.py
index 52b63d6f..d898292e 100644
--- a/tests/testcases/injector.py
+++ b/tests/testcases/injector.py
@@ -53,6 +53,7 @@ class TestInjector(unittest.TestCase):
             self.injector.stop_injecting()
             self.injector = None
         evdev.InputDevice.grab = self.grab
+        pending_events['device 2'] = []
 
     def test_modify_capabilities(self):
         class FakeDevice:
@@ -99,10 +100,9 @@ class TestInjector(unittest.TestCase):
         self.assertEqual(before, is_numlock_on())
 
     def test_injector_constructor(self):
-        global pending_events
         # this buys some time to test if the process is alive. 2 (20ms) would
         # already be enough
-        pending_events['device 2'] = [Event(1, 1, 1)] * 10
+        pending_events['device 2'] = [Event(1, 31, 1)] * 10
 
         injector2 = None
         try:
diff --git a/tests/testcases/reader.py b/tests/testcases/reader.py
new file mode 100644
index 00000000..bfe57f7f
--- /dev/null
+++ b/tests/testcases/reader.py
@@ -0,0 +1,81 @@
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+# key-mapper - GUI for device specific keyboard mappings
+# Copyright (C) 2020 sezanzeb <proxima@hip70890b.de>
+#
+# This file is part of key-mapper.
+#
+# key-mapper is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# key-mapper is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with key-mapper.  If not, see <https://www.gnu.org/licenses/>.
+
+
+import unittest
+
+import evdev
+
+from keymapper.reader import keycode_reader
+
+from test import Event, pending_events
+
+
+CODE_1 = 100
+CODE_2 = 101
+CODE_3 = 102
+
+
+class TestReader(unittest.TestCase):
+    def tearDown(self):
+        keycode_reader.clear()
+
+    def test_reading(self):
+        keycode_reader.start_reading('device 1')
+        pending_events['device 1'] = [
+            Event(evdev.events.EV_KEY, CODE_1, 1),
+            Event(evdev.events.EV_KEY, CODE_2, 1),
+            Event(evdev.events.EV_KEY, CODE_3, 1)
+        ]
+        self.assertEqual(keycode_reader.read(), CODE_3 + 8)
+        self.assertIsNone(keycode_reader.read())
+
+    def test_specific_device(self):
+        keycode_reader.start_reading('device 2')
+        pending_events['device 1'] = [
+            Event(evdev.events.EV_KEY, CODE_1, 1),
+            Event(evdev.events.EV_KEY, CODE_2, 1),
+            Event(evdev.events.EV_KEY, CODE_3, 1)
+        ]
+        self.assertIsNone(keycode_reader.read())
+
+    def test_clear(self):
+        keycode_reader.start_reading('device 1')
+        pending_events['device 1'] = [
+            Event(evdev.events.EV_KEY, CODE_1, 1),
+            Event(evdev.events.EV_KEY, CODE_2, 1),
+            Event(evdev.events.EV_KEY, CODE_3, 1)
+        ]
+        keycode_reader.clear()
+        self.assertIsNone(keycode_reader.read())
+
+    def test_switch_device(self):
+        keycode_reader.start_reading('device 2')
+        pending_events['device 2'] = [Event(evdev.events.EV_KEY, CODE_1, 1)]
+
+        keycode_reader.start_reading('device 1')
+        pending_events['device 1'] = [Event(evdev.events.EV_KEY, CODE_3, 1)]
+
+        self.assertEqual(keycode_reader.read(), CODE_3 + 8)
+        self.assertIsNone(keycode_reader.read())
+
+
+if __name__ == "__main__":
+    unittest.main()