Merge pull request #672 from mikejcurry/additional-profunctor-tests

Additional Profunctor tests covering lmap and rmap

Author: ceedubs

laws/src/main/scala/cats/laws/ProfunctorLaws.scala

@@ -17,6 +17,21 @@ trait ProfunctorLaws[F[_, _]] {
                                                     f2: A2 => A1, f1: A1 => A0,
                                                     g1: B0 => B1, g2: B1 => B2): IsEq[F[A2, B2]] =
     fab.dimap(f1)(g1).dimap(f2)(g2) <-> fab.dimap(f1 compose f2)(g2 compose g1)
+
+  def profunctorLmapIdentity[A, B](fab: F[A, B]): IsEq[F[A, B]] =
+    fab.lmap(identity[A]) <-> fab
+
+  def profunctorRmapIdentity[A, B](fab: F[A, B]): IsEq[F[A, B]] =
+    fab.rmap(identity[B]) <-> fab
+
+  def profunctorLmapComposition[A2, A1, A0, B](fab: F[A0, B],
+                                               f: A2 => A1, g: A1 => A0): IsEq[F[A2, B]] =
+    fab.lmap(g).lmap(f) <-> fab.lmap(g compose f)
+
+  def profunctorRmapComposition[A, B2, B1, B0](fab: F[A, B0],
+                                               f: B0 => B1, g: B1 => B2): IsEq[F[A, B2]] =
+    fab.rmap(f).rmap(g) <-> fab.rmap(g compose f)
+
 }
 
 object ProfunctorLaws {

laws/src/main/scala/cats/laws/discipline/ProfunctorTests.scala

@@ -15,13 +15,18 @@ trait ProfunctorTests[F[_, _]] extends Laws {
     ArbFAB: Arbitrary[F[A, B]],
     ArbFCD: Arbitrary[F[C, D]],
     EqFAB: Eq[F[A, B]],
+    EqFAD: Eq[F[A, D]],
     EqFAG: Eq[F[A, G]]
   ): RuleSet =
     new DefaultRuleSet(
       name = "profunctor",
       parent = None,
       "profunctor identity" -> forAll(laws.profunctorIdentity[A, B] _),
-      "profunctor composition" -> forAll(laws.profunctorComposition[A, B, C, D, E, G] _))
+      "profunctor composition" -> forAll(laws.profunctorComposition[A, B, C, D, E, G] _),
+      "profunctor lmap identity" -> forAll(laws.profunctorLmapIdentity[A, B] _),
+      "profunctor rmap identity" -> forAll(laws.profunctorRmapIdentity[A, B] _),
+      "profunctor lmap composition" -> forAll(laws.profunctorLmapComposition[A, B, C, D] _),
+      "profunctor rmap composition" -> forAll(laws.profunctorRmapComposition[A, D, C, B] _))
 }
 
 object ProfunctorTests {

laws/src/main/scala/cats/laws/discipline/StrongTests.scala

@@ -15,6 +15,7 @@ trait StrongTests[F[_, _]] extends ProfunctorTests[F] {
     ArbFBC: Arbitrary[F[B, C]],
     ArbFCD: Arbitrary[F[C, D]],
     EqFAB: Eq[F[A, B]],
+    EqFAD: Eq[F[A, D]],
     EqFAG: Eq[F[A, G]],
     EqFAEDE: Eq[F[(A, E), (D, E)]],
     EqFEAED: Eq[F[(E, A), (E, D)]]