Quoting Thorsten Ball: Use data that looks like data

Excellent advice from Thorsten Ball:

When debugging or testing your program, do not use data that looks like a variable or type name. 

Do not use data that looks like a label or a column name or something your operating system has tons of.

Do not use data that looks like it’s part of the program.

I would also add that using real-istic data has the advantage of testing our system under conditions that are closer to those that might be in the field.