You were a robot made for the soul purpose of seeing how GLaDOS dealt while being tasked to take care of something.

The scientists wheeled you into the room, setting you down about ten of so feet in front of GLaDOS.

“GLaDOS, this is a new robot we’ve made to see how well you can deal with taking care of something. We didn’t have the funds you provide you with a human child, so, this will have to do for now..” The scientist says, turning you on.