diff --git a/tests/test_devices.py b/tests/test_devices.py
index 9dff553..2eb7b41 100644
--- a/tests/test_devices.py
+++ b/tests/test_devices.py
@@ -13,5 +13,45 @@ from gpiozero.pins.mock import MockPin
 from gpiozero import *
 
 
-# TODO devices tests!
+# TODO add more devices tests!
+
+def test_device_no_pin():
+    with pytest.raises(GPIOPinMissing):
+        device = GPIODevice()
+
+def test_device_init():
+    pin = MockPin(2)
+    device = GPIODevice(pin)
+    assert not device.closed
+    assert device.pin == pin
+
+def test_device_init_twice_same_pin():
+    pin = MockPin(2)
+    device = GPIODevice(pin)
+    with pytest.raises(GPIOPinInUse):
+        device2 = GPIODevice(pin)
+
+def test_device_init_twice_different_pin():
+    pin = MockPin(2)
+    device = GPIODevice(pin)
+    pin2 = MockPin(3)
+    device2 = GPIODevice(pin2)
+
+def test_device_close():
+    pin = MockPin(2)
+    device = GPIODevice(pin)
+    device.close()
+    assert device.closed
+    assert device.pin is None
+
+def test_device_repr():
+    pin = MockPin(2)
+    device = GPIODevice(pin)
+    assert repr(device) == '<gpiozero.GPIODevice object on pin %s, is_active=False>' % pin
+
+def test_device_repr_after_close():
+    pin = MockPin(2)
+    device = GPIODevice(pin)
+    device.close()
+    assert repr(device) == '<gpiozero.GPIODevice object closed>'