Display status in admin console, Change the filters to include relevant fields, scopes for device status

spec/models/device_spec.rb

@@ -22,4 +22,35 @@ RSpec.describe Device, type: :model do
       expect(Device.last.next_heartbeat_time).not_to be_nil
     end
   end
+
+  describe "Device status" do
+    let!(:device){FactoryGirl.create(:device)}
+    it "Active" do
+      expect(device.status).to eql Device.statuses.keys[0]
+    end
+    it "Missing" do
+      device.update_attribute(:last_heartbeat_recd_time,Time.now - ACTIVE_TIMEFRAME)
+      expect(device.status).to eql Device.statuses.keys[1]
+    end
+    it "Dead" do
+      device.update_attribute(:last_heartbeat_recd_time,Time.now - MISSING_TIMEFRAME)
+      expect(device.status).to eql Device.statuses.keys[2]
+    end
+    describe "Scope" do
+      it "Active" do
+        expect(Device.active).to eq([device])
+      end
+      it "Missing" do
+        device.update_attribute(:last_heartbeat_recd_time,
+                                (Time.now - 15.hours))
+        expect(Device.missing).to eq([device])
+      end
+      it "Dead" do
+        device.update_attribute(:last_heartbeat_recd_time,
+                                Time.now - 1.week)
+        expect(Device.dead).to eq([device])
+      end
+    end
+  end
+
 end