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TimeMachine is an automated testing tool for Android apps, which can automatically jump to the most progressive state observed in the past when progress is slow.

TimeMachine leverages virtualization technology such as emulator to save an app state and restore it when needed. TimeMachine identifies an app state with GUI layout and memories all discovered states. When a state is considered interesting, e.g., new code is covered, TimeMachine saves the state. Meanwhile, TimeMachine observes most-recently-visited states to check whether progress is slow, e.g., being stuck in a state loop. Once progress is considered slow, TimeMachine restores the most progressive one from saved states for further exploration so that more program behavior is exercised in a short time.


author = {Dong, Zhen and B{\"o}hme, Marcel and Cojocaru, Lucia and Roychoudhury, Abhik},
title = {Time-travel Testing of Android Apps},
booktitle = {Proceedings of the 42nd International Conference on Software Engineering},
series = {ICSE '20},
year = {2020},


The figure above shows TimeMachine's architecture. The whole system runs in a docker container with the Ubuntu operating system. App under test is installed in an Android virtual machine. TimeMachine connects the virtual machine via ADB to test the app. Main Components are configured as followed:

  • Android SDK Version 25
  • Android-x86-7.1.r2
  • Virtualbox 5.1.38 or 5.0.18
  • Docker API v1.13 or above
  • Python 2.7.2


The following is required to set up TimeMachine:

  • at least 100 GB hard drive
  • 8 GB memory
  • Ububntu 16.04 64-bit

Step 1: clone repository

git clone

Step 2: install dependencies

install and configure docker

sudo apt-get install
sudo groupadd docker
sudo usermod -aG docker $USER
newgrp docker 

step 3: build an docker image

docker build -t droidtest/timemachine:1.0 .

It takes serveral minutes. Note: you should build the docker image whenever your running Linux kernel has been changed(e.g. kernel updated).


TimeMachine takes as input apks instrumented with Android apps instrumenting tool Emma or Ella. Under folder two_apps_under_test are closed-source apks instrumented with Ella, i.e., Microsoft Word and Duolingo.

cd fuzzingandroid

Test example apps in a container


./exec-single-app.bash ../two_apps_under_test/ms_word/ 0 droidtest/timemachine:1.0 1800 ../word_output
./exec-single-app.bash ../two_apps_under_test/duolingo/ 0 droidtest/timemachine:1.0 1800 ../duolingo_output


check method coverage

./compute_cov_aver.bash ../word_output/ ../two_apps_under_test/ms_word/
./compute_cov_aver.bash ../duolingo_output/ ../two_apps_under_test/duolingo/

check crashes

cat word_output/timemachine-output/crashes.log
cat duolingo_output/timemachine-output/crashes.log 

Need help?

  • If failed to connect VM, please check whether virtualbox is correctly installed. TimeMachine was tested on virtualbox 5.0.18 and virtualbox 5.1.38.
  • Contact Zhen Dong for further issues.


  • Zhen Dong (
  • Lucia Cojocaru
  • Xiao Liang Yu
  • Marcel Böhme
  • Abhik Roychoudhury
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