Validity and validity-based testing
Why?
to make writing correct software cheaper.
- Free generators
- Free shrinking
- Cheap properties
Cheap properties
- Property Combinators:
specify "inverse functions" $ inverseFunctions (+1) (-1)
specify "equivalent functions" $ equivalent ((+ 1) . (- 1)) id
specify "transitivity" $ transitivity ((>) :: Int -> Int -> Bool)
specify "symmetry" $ symmetry ((==) :: Int -> Int -> Bool)- Test suite combinators:
ordSpec @Int Ord Int
(<=) :: Int -> Int -> Bool
is reflexive for "even Int"'s
+++ OK, passed 100 tests.
is antisymmetric for "even Int"'s
+++ OK, passed 100 tests.
is transitive for "even Int"'s
+++ OK, passed 100 tests.
is equivalent to (\a b -> compare a b /= GT) for "even Int"'s
+++ OK, passed 100 tests.
(>=) :: Int -> Int -> Bool
is reflexive for "even Int"'s
+++ OK, passed 100 tests.
is antisymmetric for "even Int"'s
+++ OK, passed 100 tests.
is transitive for "even Int"'s
+++ OK, passed 100 tests.
is equivalent to (\a b -> compare a b /= LT) for "even Int"'s
+++ OK, passed 100 tests.
(<) :: Int -> Int -> Bool
is antireflexive for "even Int"'s
+++ OK, passed 100 tests.
is transitive for "even Int"'s
+++ OK, passed 100 tests.
is equivalent to (\a b -> compare a b == LT) for "even Int"'s
+++ OK, passed 100 tests.
(>) :: Int -> Int -> Bool
is antireflexive for "even Int"'s
+++ OK, passed 100 tests.
is transitive for "even Int"'s
+++ OK, passed 100 tests.
is equivalent to (\a b -> compare a b == GT) for "even Int"'s
+++ OK, passed 100 tests.
Free generators and shrinking
data MyType = MyType
{ myRational :: Rational
, myBool :: Bool
} deriving (Show, Eq, Generic)
instance Validity MyType -- Implementation is derived via Generic
instance GenValid MyType -- Default implementation via GenericgenValid :: Gen MyType -- Free generator
shrinkValid :: MyType -> [MyType] -- Free _valid_ shrinking functionCachix cache
There is a cachix cache for this project.
To use it, use cachix use validity or add the appropriate details to your nixos configuration.