ANDROID_HOME
Once you are done with Android SDK on your machine you need to set the ANDROID_HOME also when you want to execute the Mobile test automation using Appium you need to set the environment variable for ANDROID_HOME.
info
Make sure you have installed Android SDK before proceeding to next steps.
Set from Terminal
Windows
Below mention steps are for Windows machine.
ANDROID_HOME
set ANDROID_HOME=C:\ *installation location* \android-sdk
PATH
set PATH=%PATH%;%ANDROID_HOME%\tools;%ANDROID_HOME%\platform-tools
MAC OSX
Below mention steps are for Machine machine.
ANDROID_HOME
export ANDROID_HOME=/<installation location>/android-sdk-macosx
PATH
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools