How to start:

1. Download Android SDK to use adb tools.
2. Download and install GenyMotion Android Emulator (rooted)
3. Download frida-server image for Android from https://github.com/frida/frida/releases
4. Copy frida-server image file to /data/local/tmp/ path of emulator device. (you can use adb push command or just drag & drop the file)
5. Use adb shell "chmod 755 /data/local/tmp/{frida server file name}" to set proper permissions for frida-server file.
6. Run frida-server using adb shell "/data/local/tmp/{firda server file name} &" command.
7. Download and install python 3.7.
8. Create a python environment and name it what you want, then activate it.
9. In your env, use pip install frida-tools to install frida python package.
10. To see if everything works fine, in command line use frida-ps -U. this command will show a list of emulator device processes.
11. Download and install rps.apk from https://github.com/ctfs/write-ups-2015/blob/master/seccon-quals-ctf-2015/binary/reverse-engineering-android-apk-1/rps.apk
12. Run rsp app on emulator and then run python ctf.py. you will see the injected code works.

References:
https://frida.re/docs/android/
https://github.com/frida/frida/releases
https://github.com/ctfs/write-ups-2015/blob/master/seccon-quals-ctf-2015/binary/reverse-engineering-android-apk-1/rps.apk
https://book.hacktricks.xyz/mobile-apps-pentesting/android-app-pentesting/frida-tutorial
https://forum.xda-developers.com/t/official-xposed-for-lollipop-marshmallow-nougat-oreo-v90-beta3-2018-01-29.3034811/
https://labs.f-secure.com/tools/drozer/
https://github.com/m9rco/Genymotion_ARM_Translation/blob/master/package/Genymotion-ARM-Translation_for_8.0.zip