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Close #259 - Add project to test cats related code
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,36 @@ | ||
| package effectie.testing.cats | ||
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| import cats.Monad | ||
| import hedgehog.{Gen, Range} | ||
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| /** @author Kevin Lee | ||
| * @since 2021-08-04 | ||
| */ | ||
| object Gens { | ||
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| def genInt(from: Int, to: Int): Gen[Int] = | ||
| Gen.int(Range.linear(from, to)) | ||
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| def genIntFromMinToMax: Gen[Int] = Gens.genInt(Int.MinValue, Int.MaxValue) | ||
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| def genIntToInt: Gen[Int => Int] = | ||
| /* It has some hard-coded functions for now until Hedgehog has Gen[A => B] | ||
| * Reference: https://github.com/hedgehogqa/scala-hedgehog/issues/90 | ||
| */ | ||
| Gen.element1[Int => Int]( | ||
| identity[Int], | ||
| x => x + x, | ||
| x => x - x, | ||
| x => x * x, | ||
| x => x + 100, | ||
| x => x - 100, | ||
| x => x * 100 | ||
| ) | ||
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| def genAToMonadA[F[_]: Monad, A](genF: Gen[A => A]): Gen[A => F[A]] = | ||
| genF.map(f => x => Monad[F].pure(f(x))) | ||
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| def genFA[F[_]: Monad, A](genA: Gen[A]): Gen[F[A]] = | ||
| genA.map(a => Monad[F].pure(a)) | ||
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| } |
134 changes: 134 additions & 0 deletions
134
test4cats/src/main/scala/effectie/testing/cats/Laws.scala
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,134 @@ | ||
| package effectie.testing.cats | ||
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| import cats.{Applicative, Eq, Functor, Monad} | ||
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| /** @author Kevin Lee | ||
| * @since 2021-08-04 | ||
| */ | ||
| object Laws { | ||
| trait FunctorLaws { | ||
| /* Functors must preserve identity morphisms | ||
| * fmap id = id | ||
| */ | ||
| def identity[F[_], A](fa: F[A])( | ||
| implicit F: Functor[F], | ||
| FA: Eq[F[A]] | ||
| ): Boolean = | ||
| FA.eqv( | ||
| F.map(fa)(scala.Predef.identity), | ||
| fa | ||
| ) | ||
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| /* Functors preserve composition of morphisms | ||
| * fmap (f . g) == fmap f . fmap g | ||
| */ | ||
| def composition[F[_]: Functor, A, B, C](fa: F[A], f: B => C, g: A => B)( | ||
| implicit F: Functor[F], | ||
| FC: Eq[F[C]] | ||
| ): Boolean = | ||
| FC.eqv( | ||
| F.map(fa)(f compose g), | ||
| F.map(F.map(fa)(g))(f) | ||
| ) | ||
| } | ||
| object FunctorLaws extends FunctorLaws | ||
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| trait ApplicativeLaws extends FunctorLaws { | ||
| /* Identity | ||
| * pure id <*> v = v | ||
| */ | ||
| def identityAp[F[_]: Applicative, A](fa: => F[A])( | ||
| implicit F: Functor[F], | ||
| FA: Eq[F[A]] | ||
| ): Boolean = | ||
| FA.eqv( | ||
| Applicative[F].ap[A, A](Applicative[F].pure(scala.Predef.identity))(fa), | ||
| fa | ||
| ) | ||
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| /* Homomorphism | ||
| * pure f <*> pure x = pure (f x) | ||
| */ | ||
| def homomorphism[F[_]: Applicative, A, B](f: A => B, a: => A)( | ||
| implicit F: Functor[F], | ||
| FB: Eq[F[B]] | ||
| ): Boolean = | ||
| FB.eqv( | ||
| Applicative[F].ap(Applicative[F].pure(f))(Applicative[F].pure(a)), | ||
| Applicative[F].pure(f(a)) | ||
| ) | ||
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| /* Interchange | ||
| * u <*> pure y = pure ($ y) <*> u | ||
| */ | ||
| def interchange[F[_], A, B](a: => A, f: F[A => B])( | ||
| implicit F: Applicative[F], | ||
| FB: Eq[F[B]] | ||
| ): Boolean = | ||
| FB.eqv( | ||
| F.ap[A, B](f)(F.pure(a)), | ||
| F.ap[A => B, B](F.pure(g => g(a)))(f) | ||
| ) | ||
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| /* Composition | ||
| * pure (.) <*> u <*> v <*> w = u <*> (v <*> w) | ||
| */ | ||
| def compositionAp[F[_], A, B, C](fa: F[A], f: F[B => C], g: F[A => B])( | ||
| implicit F: Applicative[F], | ||
| FC: Eq[F[C]] | ||
| ): Boolean = | ||
| FC.eqv( | ||
| F.ap[A, C]( | ||
| F.ap[A => B, A => C]( | ||
| F.ap[B => C, (A => B) => (A => C)]( | ||
| F.pure(bc => ab => bc compose ab) | ||
| )(f) | ||
| )(g) | ||
| )(fa), | ||
| F.ap[B, C](f)( | ||
| F.ap[A, B](g)(fa) | ||
| ) | ||
| ) | ||
| } | ||
| object ApplicativeLaws extends ApplicativeLaws | ||
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| trait MonadLaws extends ApplicativeLaws { | ||
| /* | ||
| * return a >>= f === f a | ||
| */ | ||
| def leftIdentity[F[_], A, B](a: A, f: A => F[B])( | ||
| implicit F: Monad[F], | ||
| FB: Eq[F[B]] | ||
| ): Boolean = | ||
| FB.eqv( | ||
| F.flatMap(F.pure(a))(f), | ||
| f(a) | ||
| ) | ||
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| /* | ||
| * m >>= return === m | ||
| */ | ||
| def rightIdentity[F[_], A](fa: F[A])( | ||
| implicit F: Monad[F], | ||
| FA: Eq[F[A]] | ||
| ): Boolean = | ||
| FA.eqv( | ||
| F.flatMap(fa)(F.pure(_: A)), | ||
| fa | ||
| ) | ||
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| /* | ||
| * (m >>= f) >>= g === m >>= (\x -> f x >>= g) | ||
| */ | ||
| def associativity[F[_], A, B, C](fa: F[A], f: A => F[B], g: B => F[C])( | ||
| implicit F: Monad[F], | ||
| FC: Eq[F[C]] | ||
| ): Boolean = | ||
| FC.eqv( | ||
| F.flatMap(F.flatMap(fa)(f))(g), | ||
| F.flatMap(fa)(x => F.flatMap(f(x))(g)) | ||
| ) | ||
| } | ||
| object MonadLaws extends MonadLaws | ||
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| } |
19 changes: 19 additions & 0 deletions
19
test4cats/src/main/scala/effectie/testing/cats/MonadSpec.scala
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,19 @@ | ||
| package effectie.testing.cats | ||
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| import cats.{Eq, Monad} | ||
| import hedgehog._ | ||
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| /** @author Kevin Lee | ||
| * @since 2021-08-04 | ||
| */ | ||
| object MonadSpec { | ||
| def testLaws[F[_]: Monad](implicit eqF: Eq[F[Int]]): Property = | ||
| Specs | ||
| .monadLaws | ||
| .laws[F]( | ||
| Gens.genFA[F, Int](Gens.genInt(Int.MinValue, Int.MaxValue)), | ||
| Gens.genIntFromMinToMax, | ||
| Gens.genIntToInt, | ||
| Gens.genAToMonadA(Gens.genIntToInt) | ||
| ) | ||
| } |
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