There is a confusing facet of the concept of a specification test.
According to many textbooks, a specification test is roughly a statistical test investigating whether assumptions in a statistical model are true or not.
Here, I think, it is not clear whether specification tests are arguments for the population of interest or the data in hand.
To be specific, suppose that we imposed an assumption (or specified a model) denoted by M, and we have a data set. In this situation, a specification for M is rejected. Then, does that mean M is not appropriate to the given data? or the population?