Problem

API Tester throws this error:

apitester: error while loading shared libraries: libgtk-x11-2.0.so.0: cannot open shared object file: No such file or directory

Resolution

//
API Tester is deprecated and will be removed in a future release. API Tester is no longer installed in a Standard or Complete setup, and is only installed in a Custom setup
//
https://docs.axway.com/bundle/APIGateway_762_InstallationGuide_allOS_en_HTML5/page/Content/InstallGuideTopics/install_api_tester.htm