It is a thing of beauty. After months of meetings, charts, designs, purchase orders, assembly, phone calls, programming, and debugging...it WORKS. For an engineer, few moments are more satisfying than seeing the fruit of your labors run smoothly.
But there is a particular trap that a test engineer can fall into. Usually the system does not ship out the door - it's still there. The engineer will probably be running it, at least until he trains a technician to use it. As he uses it, he sees ways to speed it up, features to add, neat little things it could do. THIS is the trap: the test engineer spends so much time modifying/improving the system that he neglects his other tasks.
I will be honest and admit that I did this a time or two, especially when I was younger. My first love was a calorimeter I built in graduate school. I worked for months to create the right design, weeks on the code (Fortran!) to verify I was extracting the data correctly, more weeks writing software filters for the data. It was anticlimatic to actually just sit and take data and analyze that data. That's what I needed to do for my thesis - but I was happier playing with the code and the hardware. Eventually I had to force myself to do the actual testing.
Test systems are like children. They grow up and become productive - you have to let them go. But if you start taking pictures for your family album... then that's just weird.