diff --git a/sample_app/build.gradle b/sample_app/build.gradle
index 7e395bf..5cbefef 100644
--- a/sample_app/build.gradle
+++ b/sample_app/build.gradle
@@ -31,6 +31,9 @@ dependencies {
     compile 'uk.co.alt236:easycursor-android:1.0.0'
     compile fileTree(include: ['*.jar'], dir: 'libs')
     compile project(':library')
+
+    testCompile 'junit:junit:4.12'
+    testCompile 'org.mockito:mockito-all:1.9.5'
 }
 
 android {
diff --git a/sample_app/src/main/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStore.java b/sample_app/src/main/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStore.java
index acc0820..c591de7 100644
--- a/sample_app/src/main/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStore.java
+++ b/sample_app/src/main/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStore.java
@@ -1,5 +1,7 @@
 package uk.co.alt236.btlescan.containers;
 
+import android.support.annotation.NonNull;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -11,14 +13,14 @@ import uk.co.alt236.bluetoothlelib.device.BluetoothLeDevice;
 import uk.co.alt236.easycursor.objectcursor.EasyObjectCursor;
 
 public class BluetoothLeDeviceStore {
+    private static final BluetoothLeDeviceComparator DEFAULT_COMPARATOR = new BluetoothLeDeviceComparator();
     private final Map<String, BluetoothLeDevice> mDeviceMap;
 
-
     public BluetoothLeDeviceStore() {
         mDeviceMap = new HashMap<>();
     }
 
-    public void addDevice(final BluetoothLeDevice device) {
+    public void addDevice(@NonNull final BluetoothLeDevice device) {
         if (mDeviceMap.containsKey(device.getAddress())) {
             mDeviceMap.get(device.getAddress()).updateRssiReading(device.getTimestamp(), device.getRssi());
         } else {
@@ -30,24 +32,42 @@ public class BluetoothLeDeviceStore {
         mDeviceMap.clear();
     }
 
+    public int getSize() {
+        return mDeviceMap.size();
+    }
+
+    @NonNull
     public EasyObjectCursor<BluetoothLeDevice> getDeviceCursor() {
+        return getDeviceCursor(DEFAULT_COMPARATOR);
+    }
+
+    @NonNull
+    public EasyObjectCursor<BluetoothLeDevice> getDeviceCursor(@NonNull Comparator<BluetoothLeDevice> comparator) {
         return new EasyObjectCursor<>(
                 BluetoothLeDevice.class,
-                getDeviceList(),
+                getDeviceList(comparator),
                 "address");
     }
 
+    @NonNull
     public List<BluetoothLeDevice> getDeviceList() {
+        return getDeviceList(DEFAULT_COMPARATOR);
+    }
+
+    @NonNull
+    public List<BluetoothLeDevice> getDeviceList(@NonNull Comparator<BluetoothLeDevice> comparator) {
         final List<BluetoothLeDevice> methodResult = new ArrayList<>(mDeviceMap.values());
 
-        Collections.sort(methodResult, new Comparator<BluetoothLeDevice>() {
-
-            @Override
-            public int compare(final BluetoothLeDevice arg0, final BluetoothLeDevice arg1) {
-                return arg0.getAddress().compareToIgnoreCase(arg1.getAddress());
-            }
-        });
+        Collections.sort(methodResult, comparator);
 
         return methodResult;
     }
+
+    private static class BluetoothLeDeviceComparator implements Comparator<BluetoothLeDevice> {
+
+        @Override
+        public int compare(final BluetoothLeDevice arg0, final BluetoothLeDevice arg1) {
+            return arg0.getAddress().compareTo(arg1.getAddress());
+        }
+    }
 }
diff --git a/sample_app/src/test/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStoreTest.java b/sample_app/src/test/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStoreTest.java
new file mode 100644
index 0000000..0ab71e0
--- /dev/null
+++ b/sample_app/src/test/java/uk/co/alt236/btlescan/containers/BluetoothLeDeviceStoreTest.java
@@ -0,0 +1,88 @@
+package uk.co.alt236.btlescan.containers;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import uk.co.alt236.bluetoothlelib.device.BluetoothLeDevice;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+public class BluetoothLeDeviceStoreTest {
+    private BluetoothLeDeviceStore cut;
+
+    @Before
+    public void setUp() {
+        cut = new BluetoothLeDeviceStore();
+    }
+
+    @Test
+    public void testAddOne() {
+        assertStoreSize(0);
+
+        cut.addDevice(createDevice("foo"));
+        assertStoreSize(1);
+
+        cut.clear();
+        assertStoreSize(0);
+    }
+
+    @Test
+    public void testAddTwo() {
+        assertStoreSize(0);
+
+        cut.addDevice(createDevice("foo"));
+        assertStoreSize(1);
+
+        cut.addDevice(createDevice("bar"));
+        assertStoreSize(2);
+
+        cut.clear();
+        assertStoreSize(0);
+    }
+
+    @Test
+    public void testUpdateOne() {
+        assertStoreSize(0);
+
+        cut.addDevice(createDevice("foo", 100, 101));
+        assertStoreSize(1);
+        final BluetoothLeDevice device1 = cut.getDeviceList().get(0);
+        assertEquals(100, device1.getTimestamp());
+        assertEquals(101, device1.getRssi());
+
+        cut.addDevice(createDevice("foo", 200, 201));
+        assertStoreSize(1);
+        final BluetoothLeDevice device2 = cut.getDeviceList().get(0);
+        assertSame(device1, device2);
+        Mockito
+                .verify(device2, Mockito.times(1))
+                .updateRssiReading(200, 201);
+
+        cut.clear();
+        assertStoreSize(0);
+    }
+
+
+    private BluetoothLeDevice createDevice(final String mac) {
+        final BluetoothLeDevice mock = Mockito.mock(BluetoothLeDevice.class);
+        return createDevice(mac, 0, 0);
+    }
+
+    private BluetoothLeDevice createDevice(final String mac, long rssiTime, int rssi) {
+        final BluetoothLeDevice mock = Mockito.mock(BluetoothLeDevice.class);
+
+        Mockito.when(mock.getAddress()).thenReturn(mac);
+        Mockito.when(mock.getTimestamp()).thenReturn(rssiTime);
+        Mockito.when(mock.getRssi()).thenReturn(rssi);
+
+        return mock;
+    }
+
+    private void assertStoreSize(final int expected) {
+        assertEquals(expected, cut.getSize());
+        assertEquals(expected, cut.getDeviceCursor().getCount());
+        assertEquals(expected, cut.getDeviceList().size());
+    }
+}
\ No newline at end of file