In this article, the author explores what Assessing Pupils' Progress (APP) is about. He contends that the predilection for testing is a catastrophe as far as the teaching and learning of mathematics is concerned; it is an outcome of the drive for collecting so-called "data" on pupils. What those people, who should know better, either choose to ignore or even worse believe in, is that the data collected from test scores has any meaning whatsoever with regard to assessing pupils' mathematics; testing is a fundamentally flawed process and tells nothing about achievement, understanding or the application of mathematics.