More dependencies and test instead of run

src/bin/cli_app.rs

@@ -16,4 +16,13 @@ fn main() {
         }
     };
     println!("Battery level: {}%", battery_level);
+}
+
+#[test]
+fn test_basic_device_access() {
+    let mut device = match Device::new() {
+        Ok(device) => device,
+        Err(error) => return
+    };
+    device.update_battery_level();
 }