Appian Automation Tool

You can use FitNesse, Cucumber or Selenium API for automated testing. Refer to https://docs.appian.com/suite/help/21.1/testing-applications.html

Pranavi, are you trying to automate your development as in automating the testing of expression rules? or you want to automate Appian UI?

If you want to look for 1st then look for Expression Rule Testing

If you want to automate the functional tests then Fitnesse for Appian / Cucumber for Appian will be a good choice. Refer below links 

1. https://community.appian.com/w/the-appian-playbook/97/automated-testing-with-fitnesse-for-appian

2. https://community.appian.com/w/the-appian-playbook/1325/automated-testing-with-cucumber-for-appian

3. https://community.appian.com/w/the-appian-playbook/2304/automated-testing-with-appian-selenium-api

Let me know if you need any more assistance in Appian Automation testing 

Thanks