"It is practically impossible to teach good programming style to students that have had prior exposure to BASIC.
As potential programmers, they are mentally mutilated beyond hope of regeneration." [E. W. Dijkstra]
I studied computer science as a secondary subject and I worked as a systems programmer later on. When I entered the banking industry I almost fainted. Programs were of quite poor quality. Many programmers in the '80s have never heard of Jon Bentley's Programming Pearls.
Then Excel © was distributed and each and every hobby programmer offered his "solutions" to the public. I had to face the fact that many programs and many worksheets were not tested before shipping.
The application below is meant to help people who want to test properly. This is just the first initial idea. I am thinking about defining all inputs via XML.