FitSpec provides automated assistance in the task of refining test properties for Haskell functions. FitSpec tests mutant variations of functions under test against a given property set, recording any surviving mutants that pass all tests. FitSpec then reports: surviving mutants: indicating incompleteness of properties, prompting the user to amend a property or to add a new one; conjectures: indicating redundancy in the property set, prompting the user to remove properties so to reduce the cost of testing.