Nicole Schmidt


Bug hunters of the Corona Warn App

In mid-June, the Corona warning app of the German government was launched. It was implemented by the two partners SAP and Deutsche Telekom. The app is now downloaded to 17 million devices.

Dresden test center

In the Dresden test center, the bug hunters have the Corona warning app on dozens of different smartphones in view around the clock.

The 17 million consist of iPhones from Apple and Android devices from various manufacturers, each with various personal settings. Despite careful programming work, hick-ups are not excluded. The Corona Warn App is part of a complex technological overall system with a completely new interface, which, however, gets better and better over time. Every day we work on further improving the app. This is something that is quite common in the world of software. Even the most successful apps have one to four releases per month and with each release not only new features are introduced but bugs are also fixed.

Part of the optimization work takes place in Telekom's test center in Dresden. Here, the bug hunters are tapping into various functionalities on dozens of the most common smartphone types. This is done with automated tests. This allows many points to be checked in the shortest possible time. A classic example is the download: Which individual settings on the devices (battery settings, background update on/off, etc.) cause difficulties during app installation? The bug hunters monitor the interaction of all components in practice and can pick up unforeseen functional restrictions - no matter where they come from - faster. However, the opposite approach is also important, namely the reproduction of problems reported by users.

Only if a bug is reproduced can a way to solve it be found. A current example is a problem after the iOS 1.2.0 update: More and more users reported app crashes after the release update. The analysis of the error message showed that on these devices the background update was disabled during the update and thus caused an app crash. The SAP and Telekom development team programmed a hotfix to fix the problem. Only a few hours later, the hotfix was available for users in the App Store.

The Corona Warning App works best if you follow these instructions

  • Load current software (1.2.1 Android or 1.2.1 iOS)
  • Update operating system regularly (iOS 13.6.1 or Android 6 with Google Play Services)
  • Always switch on and check background updating
  • To be on the safe side, open the app once a day after 24 hours.


Information related to the Covid-19 pandemic and the Corona Warn App in the years 2020 and 2021.