Obviously not. Suppose the input to my function is a 64-bit integer. My test cannot possibly try every possible 64-bit integer. It would take years for such a test to finish.
This is why tools like formal verification and symbolic analyses can help you establish that for all possible integers X, your function does the right thing (for some definition of “right”). You get this assurance without having to actually enumerate all X.
This is why tools like formal verification and symbolic analyses can help you establish that for all possible integers X, your function does the right thing (for some definition of “right”). You get this assurance without having to actually enumerate all X.