From f12726306d5778c5b7d3293c8f683845f2748459 Mon Sep 17 00:00:00 2001
From: Travis Brown <travisrobertbrown@gmail.com>
Date: Wed, 29 Jan 2020 12:25:03 +0000
Subject: [PATCH 1/5] Add ioTimer and ioContextShift test helpers

---
 .../internals/IOContextShiftTests.scala       |  2 +-
 .../cats/effect/laws/util/TestContext.scala   | 12 ++-
 .../effect/ConcurrentCancelableFTests.scala   | 12 +--
 .../effect/ConcurrentContinualTests.scala     | 12 +--
 .../scala/cats/effect/ContextShiftTests.scala | 30 +++----
 .../test/scala/cats/effect/FiberTests.scala   | 22 ++---
 .../scala/cats/effect/IOCancelableTests.scala |  8 +-
 .../src/test/scala/cats/effect/IOTests.scala  | 82 +++++++++----------
 .../scala/cats/effect/InstancesTests.scala    | 19 +++--
 .../test/scala/cats/effect/MemoizeTests.scala | 18 ++--
 .../scala/cats/effect/ResourceTests.scala     | 10 +--
 .../scala/cats/effect/TestContextTests.scala  |  4 +-
 12 files changed, 122 insertions(+), 109 deletions(-)

diff --git a/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala b/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala
index a9e7986a3b..e5078ad43e 100644
--- a/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala
+++ b/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala
@@ -21,7 +21,7 @@ import scala.util.Success
 
 class IOContextShiftTests extends BaseTestsSuite {
   testAsync("ContextShift[IO] instance based on implicit ExecutionContext") { implicit ec =>
-    val contextShift = ec.contextShift[IO]
+    val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = contextShift.shift.map(_ => 1).unsafeToFuture()
     f.value shouldBe None
diff --git a/laws/shared/src/main/scala/cats/effect/laws/util/TestContext.scala b/laws/shared/src/main/scala/cats/effect/laws/util/TestContext.scala
index a1ad6a827c..a8705a42e0 100644
--- a/laws/shared/src/main/scala/cats/effect/laws/util/TestContext.scala
+++ b/laws/shared/src/main/scala/cats/effect/laws/util/TestContext.scala
@@ -135,6 +135,11 @@ final class TestContext private () extends ExecutionContext { self =>
     lastReportedFailure = None
   )
 
+  /**
+   * Derives a `cats.effect.Timer` from this `TestContext` for `IO`.
+   */
+  def ioTimer: Timer[IO] = timer[IO](IO.ioEffect)
+
   /**
    * Derives a `cats.effect.Timer` from this `TestContext`, for any data
    * type that has a `LiftIO` instance.
@@ -165,9 +170,14 @@ final class TestContext private () extends ExecutionContext { self =>
       }
     }
 
+  /**
+   * Derives a `cats.effect.ContextShift` from this `TestContext` for `IO`.
+   */
+  def ioContextShift: ContextShift[IO] = contextShift[IO](IO.ioEffect)
+
   /**
    * Derives a `cats.effect.ContextShift` from this `TestContext`, for any data
-   * type that has a `LiftIO` and `MonadError` instance.
+   * type that has an `Async` instance.
    *
    * Example:
    *
diff --git a/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala b/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala
index a041c93a12..0dfbdfaeee 100644
--- a/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala
@@ -27,7 +27,7 @@ import scala.util.Success
 
 class ConcurrentCancelableFTests extends BaseTestsSuite {
   testAsync("Concurrent.cancelableF works for immediate values") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (value: Either[Throwable, Int]) =>
       val received = Concurrent.cancelableF[IO, Int](cb => IO { cb(value); IO.unit })
@@ -36,7 +36,7 @@ class ConcurrentCancelableFTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.cancelableF works for async values") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (value: Either[Throwable, Int]) =>
       val received = Concurrent.cancelableF[IO, Int] { cb =>
@@ -48,7 +48,7 @@ class ConcurrentCancelableFTests extends BaseTestsSuite {
 
   testAsync("Concurrent.cancelableF can delay callback") { implicit ec =>
     import scala.concurrent.duration._
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val timer = ec.timer[IO]
 
     val task = Concurrent.cancelableF[IO, Int] { cb =>
@@ -70,7 +70,7 @@ class ConcurrentCancelableFTests extends BaseTestsSuite {
 
   testAsync("Concurrent.cancelableF can delay task execution") { implicit ec =>
     import scala.concurrent.duration._
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val timer = ec.timer[IO]
 
     val complete = Promise[Unit]()
@@ -89,7 +89,7 @@ class ConcurrentCancelableFTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.cancelableF can yield cancelable tasks") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val task = for {
       d <- MVar.empty[IO, Unit]
@@ -114,7 +114,7 @@ class ConcurrentCancelableFTests extends BaseTestsSuite {
   testAsync("Concurrent.cancelableF executes generated task uninterruptedly") { implicit ec =>
     import scala.concurrent.duration._
 
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     var effect = 0
diff --git a/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala b/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala
index 3872e8b8ca..829149e519 100644
--- a/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala
@@ -24,7 +24,7 @@ import scala.util.Success
 class ConcurrentContinualTests extends BaseTestsSuite {
   testAsync("Concurrent.continual allows interruption of its input") { implicit ec =>
     import scala.concurrent.duration._
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val task = Ref[IO].of(false).flatMap { canceled =>
@@ -42,7 +42,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
 
   testAsync("Concurrent.continual backpressures on finalizers") { implicit ec =>
     import scala.concurrent.duration._
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val task = Ref[IO].of(false).flatMap { canceled =>
@@ -63,7 +63,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.continual behaves like flatMap on the happy path") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val task = IO(1).continual(n => IO(n.toOption.get + 1)).map(_ + 1)
 
     val f = task.unsafeToFuture()
@@ -72,7 +72,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.continual behaves like handleErrorWith on errors") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val ex = new Exception("boom")
     val task = IO.raiseError[Unit](ex).continual(n => IO(n.swap.toOption.get))
@@ -83,7 +83,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.continual propagates errors in the continuation") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val ex = new Exception("boom")
     val task = IO(1).continual(_ => IO.raiseError(ex)).handleError(identity)
@@ -95,7 +95,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
 
   testAsync("Concurrent.continual respects the continual guarantee") { implicit ec =>
     import scala.concurrent.duration._
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val task = Ref[IO].of(false).flatMap { completed =>
diff --git a/laws/shared/src/test/scala/cats/effect/ContextShiftTests.scala b/laws/shared/src/test/scala/cats/effect/ContextShiftTests.scala
index ae75913b6b..1526ecc24a 100644
--- a/laws/shared/src/test/scala/cats/effect/ContextShiftTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ContextShiftTests.scala
@@ -30,7 +30,7 @@ class ContextShiftTests extends BaseTestsSuite {
   type IorTIO[A] = IorT[IO, Int, A]
 
   testAsync("ContextShift[IO].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val f = cs.shift.unsafeToFuture()
     f.value shouldBe None
@@ -40,7 +40,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("ContextShift[IO].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val ec2 = TestContext()
 
     val f = cs.evalOn(ec2)(IO(1)).unsafeToFuture()
@@ -56,7 +56,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("ContextShift.evalOnK[IO]") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val ec2 = TestContext()
 
     val funK = ContextShift.evalOnK[IO](ec2)
@@ -75,7 +75,7 @@ class ContextShiftTests extends BaseTestsSuite {
   // -- EitherT
 
   testAsync("Timer[EitherT].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val f = implicitly[ContextShift[EitherTIO]].shift.value.unsafeToFuture()
 
     f.value shouldBe None
@@ -85,7 +85,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("Timer[EitherT].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val cs2 = implicitly[ContextShift[EitherTIO]]
     val ec2 = TestContext()
 
@@ -104,7 +104,7 @@ class ContextShiftTests extends BaseTestsSuite {
   // -- OptionT
 
   testAsync("Timer[OptionT].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val f = implicitly[ContextShift[OptionTIO]].shift.value.unsafeToFuture()
 
     f.value shouldBe None
@@ -114,7 +114,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("Timer[OptionT].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val cs2 = implicitly[ContextShift[OptionTIO]]
     val ec2 = TestContext()
 
@@ -133,7 +133,7 @@ class ContextShiftTests extends BaseTestsSuite {
   // -- WriterT
 
   testAsync("Timer[WriterT].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val f = implicitly[ContextShift[WriterTIO]].shift.value.unsafeToFuture()
 
     f.value shouldBe None
@@ -143,7 +143,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("Timer[WriterT].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val cs2 = implicitly[ContextShift[WriterTIO]]
     val ec2 = TestContext()
 
@@ -162,7 +162,7 @@ class ContextShiftTests extends BaseTestsSuite {
   // -- StateT
 
   testAsync("Timer[StateT].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val f = implicitly[ContextShift[StateTIO]].shift.run(0).unsafeToFuture()
 
     f.value shouldBe None
@@ -172,7 +172,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("Timer[StateT].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val cs2 = implicitly[ContextShift[StateTIO]]
     val ec2 = TestContext()
 
@@ -191,7 +191,7 @@ class ContextShiftTests extends BaseTestsSuite {
   // -- Kleisli
 
   testAsync("Timer[Kleisli].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val f = implicitly[ContextShift[KleisliIO]].shift.run(0).unsafeToFuture()
 
     f.value shouldBe None
@@ -201,7 +201,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("Timer[Kleisli].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val cs2 = implicitly[ContextShift[KleisliIO]]
     val ec2 = TestContext()
 
@@ -220,7 +220,7 @@ class ContextShiftTests extends BaseTestsSuite {
   // -- IorT
 
   testAsync("Timer[IorT].shift") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val f = implicitly[ContextShift[IorTIO]].shift.value.unsafeToFuture()
 
     f.value shouldBe None
@@ -230,7 +230,7 @@ class ContextShiftTests extends BaseTestsSuite {
   }
 
   testAsync("Timer[IorT].evalOn") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val cs2 = implicitly[ContextShift[IorTIO]]
     val ec2 = TestContext()
 
diff --git a/laws/shared/src/test/scala/cats/effect/FiberTests.scala b/laws/shared/src/test/scala/cats/effect/FiberTests.scala
index 19c5a0dc0b..18158488e4 100644
--- a/laws/shared/src/test/scala/cats/effect/FiberTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/FiberTests.scala
@@ -34,22 +34,22 @@ class FiberTests extends BaseTestsSuite {
     Eq.by[Fiber[F, A], F[A]](_.join)
 
   checkAllAsync("Fiber[IO, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     ApplicativeTests[Fiber[IO, *]].applicative[Int, Int, Int]
   })
 
   checkAllAsync("Fiber[IO, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     SemigroupTests[Fiber[IO, Int]](Fiber.fiberSemigroup[IO, Int]).semigroup
   })
 
   checkAllAsync("Fiber[IO, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     MonoidTests[Fiber[IO, Int]].monoid
   })
 
   testAsync("Canceling join does not cancel the source fiber") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     var fiberCanceled = false
     var joinCanceled = false
@@ -84,7 +84,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Applicative[Fiber[IO, *].map2 preserves both cancelation tokens") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     var canceled = 0
 
     // Needs latches due to IO being auto-cancelable at async boundaries
@@ -112,7 +112,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Applicative[Fiber[IO, *].map2 cancels first, when second terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -139,7 +139,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Applicative[Fiber[IO, *].map2 cancels second, when first terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -165,7 +165,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Monoid[Fiber[IO, *].combine cancels first, when second terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -191,7 +191,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Monoid[Fiber[IO, *].combine cancels second, when first terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -217,7 +217,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Semigroup[Fiber[IO, *].combine cancels first, when second terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -243,7 +243,7 @@ class FiberTests extends BaseTestsSuite {
   }
 
   testAsync("Semigroup[Fiber[IO, *].combine cancels second, when first terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
diff --git a/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala b/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
index 84392261c3..59a2fe795e 100644
--- a/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
@@ -36,7 +36,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("IO.cancelBoundary can be canceled") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val f = (IO.shift *> IO.cancelBoundary).unsafeToFuture()
     f.value shouldBe None
@@ -51,7 +51,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("(fa <* IO.cancelBoundary).cancel <-> IO.never") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (fa: IO[Int]) =>
       val received =
@@ -66,7 +66,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("task.start.flatMap(id) <-> task") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (task: IO[Int]) =>
       task.start.flatMap(_.join) <-> task
@@ -74,7 +74,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("task.start is cancelable") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val task = (IO.shift *> IO.cancelBoundary *> IO(1)).start.flatMap(_.join)
 
diff --git a/laws/shared/src/test/scala/cats/effect/IOTests.scala b/laws/shared/src/test/scala/cats/effect/IOTests.scala
index 09f545c568..a81dc29a9f 100644
--- a/laws/shared/src/test/scala/cats/effect/IOTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOTests.scala
@@ -36,7 +36,7 @@ import scala.concurrent.duration._
 
 class IOTests extends BaseTestsSuite {
   checkAllAsync("IO", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     ConcurrentEffectTests[IO].concurrentEffect[Int, Int, Int]
   })
 
@@ -45,19 +45,19 @@ class IOTests extends BaseTestsSuite {
   checkAllAsync("IO", implicit ec => AlignTests[IO].align[Int, Int, Int, Int])
 
   checkAllAsync("IO.Par", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     CommutativeApplicativeTests[IO.Par].commutativeApplicative[Int, Int, Int]
   })
 
   checkAllAsync("IO.Par", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     AlignTests[IO.Par].align[Int, Int, Int, Int]
   })
 
   checkAllAsync(
     "IO",
     implicit ec => {
-      implicit val cs = ec.contextShift[IO]
+      implicit val cs: ContextShift[IO] = ec.ioContextShift
 
       // do NOT inline this val; it causes the 2.13.0 compiler to crash for... reasons (see: scala/bug#11732)
       val module = ParallelTests[IO]
@@ -73,14 +73,14 @@ class IOTests extends BaseTestsSuite {
   checkAllAsync(
     "IO(ConcurrentEffect defaults)",
     implicit ec => {
-      implicit val cs = ec.contextShift[IO]
+      implicit val cs: ContextShift[IO] = ec.ioContextShift
       implicit val ioConcurrent = IOTests.ioConcurrentEffectDefaults(ec)
       ConcurrentEffectTests[IO].concurrentEffect[Int, Int, Int]
     }
   )
 
   testAsync("IO.Par's applicative instance is different") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicitly[Applicative[IO]] shouldNot be(implicitly[Applicative[IO.Par]])
   }
 
@@ -175,7 +175,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("shift works for success (via Timer)") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val expected = IO.shift.flatMap(_ => IO(1)).unsafeToFuture()
     expected.value shouldEqual None
@@ -193,7 +193,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("shift works for failure (via Timer)") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val dummy = new RuntimeException("dummy")
 
     val expected = IO.shift.flatMap(_ => IO.raiseError(dummy)).unsafeToFuture()
@@ -536,7 +536,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 for successful values") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val io1 = IO.shift *> IO.pure(1)
     val io2 = IO.shift *> IO.pure(2)
@@ -548,7 +548,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 can fail for one") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     val io1 = IO.shift *> IO.pure(1)
@@ -568,7 +568,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 can fail for both, with non-deterministic failure") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     catchSystemErr {
       val dummy1 = new RuntimeException("dummy1")
@@ -586,7 +586,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 is stack safe") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 100000 else 5000
     val io = (0 until count).foldLeft(IO(0))((acc, e) => (acc, IO(e)).parMapN(_ + _))
@@ -597,7 +597,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 cancels first, when second terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -616,7 +616,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 cancels second, when first terminates in error") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val dummy = new RuntimeException("dummy")
     var wasCanceled = false
@@ -635,7 +635,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("IO.cancelable IOs can be canceled") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     var wasCanceled = false
     val p = Promise[Int]()
@@ -680,7 +680,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("IO.timeout can mirror the source") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     check { (ioa: IO[Int]) =>
@@ -689,7 +689,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("IO.timeout can end in timeout") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val task = for {
@@ -759,7 +759,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("bracket does not evaluate use on cancel") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     var use = false
@@ -784,7 +784,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("racePair should be stack safe, take 1") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 100000 else 1000
     val tasks = (0 until count).map(_ => IO.shift *> IO(1))
@@ -804,7 +804,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("racePair should be stack safe, take 2") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 100000 else 1000
     val tasks = (0 until count).map(_ => IO(1))
@@ -824,7 +824,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("racePair has a stack safe cancelable") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 10000 else 1000
     val p = Promise[Int]()
@@ -854,7 +854,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("racePair avoids extraneous async boundaries") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = IO
       .racePair(IO.shift *> IO(1), IO.shift *> IO(1))
@@ -872,7 +872,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("race should be stack safe, take 1") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 100000 else 1000
     val tasks = (0 until count).map(_ => IO.shift *> IO(1))
@@ -892,7 +892,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("race should be stack safe, take 2") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 100000 else 1000
     val tasks = (0 until count).map(_ => IO(1))
@@ -912,7 +912,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("race has a stack safe cancelable") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 10000 else 1000
     val p = Promise[Int]()
@@ -939,7 +939,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("race forks execution") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = IO
       .race(IO(1), IO(1))
@@ -956,7 +956,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("race avoids extraneous async boundaries") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = IO
       .race(IO.shift *> IO(1), IO.shift *> IO(1))
@@ -973,7 +973,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 should be stack safe") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 100000 else 1000
     val tasks = (0 until count).map(_ => IO(1))
@@ -985,7 +985,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 has a stack safe cancelable") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val count = if (IOPlatform.isJVM) 10000 else 1000
     val tasks = (0 until count).map(_ => IO.never: IO[Int])
@@ -1004,7 +1004,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 forks execution") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = (IO(1), IO(1)).parMapN(_ + _).unsafeToFuture()
     f.value shouldBe None
@@ -1017,7 +1017,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("parMap2 avoids extraneous async boundaries") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = (IO.shift *> IO(1), IO.shift *> IO(1))
       .parMapN(_ + _)
@@ -1033,7 +1033,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("start forks automatically") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = IO(1).start.flatMap(_.join).unsafeToFuture()
     f.value shouldBe None
@@ -1042,7 +1042,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("start avoids async boundaries") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = (IO.shift *> IO(1)).start.flatMap(_.join).unsafeToFuture()
     f.value shouldBe None
@@ -1051,7 +1051,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("background cancels the action in cleanup") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = Deferred[IO, Unit]
       .flatMap { started => //wait for this before closing resource
@@ -1069,7 +1069,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("background allows awaiting the action") { ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
 
     val f = Deferred[IO, Unit]
       .flatMap { latch =>
@@ -1085,7 +1085,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("cancel should wait for already started finalizers on success") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val fa = for {
@@ -1105,7 +1105,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("cancel should wait for already started finalizers on failure") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val dummy = new RuntimeException("dummy")
@@ -1127,7 +1127,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("cancel should wait for already started use finalizers") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val fa = for {
@@ -1151,7 +1151,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("second cancel should wait for use finalizers") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val fa = for {
@@ -1175,7 +1175,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("second cancel during acquire should wait for it and finalizers to complete") { implicit ec =>
-    implicit val contextShift = ec.contextShift[IO]
+    implicit val contextShift: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val fa = for {
@@ -1201,7 +1201,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("second cancel during acquire should wait for it and finalizers to complete (non-terminating)") {
     implicit ec =>
-      implicit val contextShift = ec.contextShift[IO]
+      implicit val contextShift: ContextShift[IO] = ec.ioContextShift
       implicit val timer = ec.timer[IO]
 
       val fa = for {
diff --git a/laws/shared/src/test/scala/cats/effect/InstancesTests.scala b/laws/shared/src/test/scala/cats/effect/InstancesTests.scala
index d9c03a80f8..78435e1f0f 100644
--- a/laws/shared/src/test/scala/cats/effect/InstancesTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/InstancesTests.scala
@@ -36,7 +36,7 @@ class InstancesTests extends BaseTestsSuite {
   )
 
   checkAllAsync("OptionT[IO, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     ConcurrentTests[OptionT[IO, *]].concurrent[Int, Int, Int]
   })
 
@@ -49,7 +49,7 @@ class InstancesTests extends BaseTestsSuite {
   )
 
   checkAllAsync("Kleisli[IO, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     ConcurrentTests[Kleisli[IO, Int, *]].concurrent[Int, Int, Int]
   })
 
@@ -58,7 +58,7 @@ class InstancesTests extends BaseTestsSuite {
   checkAllAsync(
     "EitherT[IO, Throwable, *]",
     implicit ec => {
-      implicit val cs = ec.contextShift[IO]
+      implicit val cs: ContextShift[IO] = ec.ioContextShift
       ConcurrentEffectTests[EitherT[IO, Throwable, *]].concurrentEffect[Int, Int, Int]
     }
   )
@@ -71,10 +71,13 @@ class InstancesTests extends BaseTestsSuite {
     }
   )
 
-  checkAllAsync("WriterT[IO, Int, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
-    ConcurrentEffectTests[WriterT[IO, Int, *]].concurrentEffect[Int, Int, Int]
-  })
+  checkAllAsync(
+    "WriterT[IO, Int, *]",
+    implicit ec => {
+      implicit val cs: ContextShift[IO] = ec.ioContextShift
+      ConcurrentEffectTests[WriterT[IO, Int, *]].concurrentEffect[Int, Int, Int]
+    }
+  )
 
   checkAllAsync(
     "WriterT[IO, Int, *]",
@@ -85,7 +88,7 @@ class InstancesTests extends BaseTestsSuite {
   )
 
   checkAllAsync("IorT[IO, Int, *]", implicit ec => {
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     ConcurrentTests[IorT[IO, Int, *]].concurrent[Int, Int, Int]
   })
 
diff --git a/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala b/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
index ed7ecd0c28..db05a3b023 100644
--- a/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
@@ -28,7 +28,7 @@ import cats.laws.discipline._
 
 class MemoizeTests extends BaseTestsSuite {
   testAsync("Concurrent.memoize does not evaluates the effect if the inner `F[A]`isn't bound") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     val timer = ec.timer[IO]
 
     val prog = for {
@@ -45,7 +45,7 @@ class MemoizeTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.memoize evalutes effect once if inner `F[A]` is bound twice") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val prog = for {
       ref <- Ref.of[IO, Int](0)
@@ -66,7 +66,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Concurrent.memoize effect evaluates effect once if the inner `F[A]` is bound twice (race)") {
     implicit ec =>
-      implicit val cs = ec.contextShift[IO]
+      implicit val cs: ContextShift[IO] = ec.ioContextShift
       val timer = ec.timer[IO]
 
       val prog = for {
@@ -88,14 +88,14 @@ class MemoizeTests extends BaseTestsSuite {
   }
 
   testAsync("Concurrent.memoize and then flatten is identity") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     check { fa: IO[Int] =>
       Concurrent.memoize(fa).flatten <-> fa
     }
   }
 
   testAsync("Memoized effects can be canceled when there are no other active subscribers (1)") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val prog = for {
@@ -115,7 +115,7 @@ class MemoizeTests extends BaseTestsSuite {
   }
 
   testAsync("Memoized effects can be canceled when there are no other active subscribers (2)") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val prog = for {
@@ -138,7 +138,7 @@ class MemoizeTests extends BaseTestsSuite {
   }
 
   testAsync("Memoized effects can be canceled when there are no other active subscribers (3)") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val prog = for {
@@ -161,7 +161,7 @@ class MemoizeTests extends BaseTestsSuite {
   }
 
   testAsync("Running a memoized effect after it was previously canceled reruns it") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val prog = for {
@@ -183,7 +183,7 @@ class MemoizeTests extends BaseTestsSuite {
   }
 
   testAsync("Attempting to cancel a memoized effect with active subscribers is a no-op") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
     implicit val timer = ec.timer[IO]
 
     val prog = for {
diff --git a/laws/shared/src/test/scala/cats/effect/ResourceTests.scala b/laws/shared/src/test/scala/cats/effect/ResourceTests.scala
index 35c521cbb4..cb56bb5c87 100644
--- a/laws/shared/src/test/scala/cats/effect/ResourceTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ResourceTests.scala
@@ -97,8 +97,8 @@ class ResourceTests extends BaseTestsSuite {
   }
 
   testAsync("liftF - interruption") { implicit ec =>
-    implicit val timer = ec.timer[IO]
-    implicit val ctx = ec.contextShift[IO]
+    implicit val timer: Timer[IO] = ec.ioTimer
+    implicit val ctx: ContextShift[IO] = ec.ioContextShift
 
     def p =
       Deferred[IO, ExitCase[Throwable]]
@@ -135,7 +135,7 @@ class ResourceTests extends BaseTestsSuite {
 
   testAsync("(evalMap with error <-> IO.raiseError") { implicit ec =>
     case object Foo extends Exception
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (g: Int => IO[Int]) =>
       val effect: Int => IO[Int] = a => (g(a) <* IO(throw Foo))
@@ -150,7 +150,7 @@ class ResourceTests extends BaseTestsSuite {
   }
 
   testAsync("evalTap with cancellation <-> IO.never") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (g: Int => IO[Int]) =>
       val effect: Int => IO[Int] = a =>
@@ -166,7 +166,7 @@ class ResourceTests extends BaseTestsSuite {
 
   testAsync("(evalTap with error <-> IO.raiseError") { implicit ec =>
     case object Foo extends Exception
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     check { (g: Int => IO[Int]) =>
       val effect: Int => IO[Int] = a => (g(a) <* IO(throw Foo))
diff --git a/laws/shared/src/test/scala/cats/effect/TestContextTests.scala b/laws/shared/src/test/scala/cats/effect/TestContextTests.scala
index ee9b165675..6514268997 100644
--- a/laws/shared/src/test/scala/cats/effect/TestContextTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/TestContextTests.scala
@@ -90,7 +90,7 @@ class TestContextTests extends BaseTestsSuite {
   }
 
   testAsync("IO.shift via implicit ExecutionContext") { implicit ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val f = IO.shift.flatMap(_ => IO(1 + 1)).unsafeToFuture()
     assert(f.value === None)
@@ -100,7 +100,7 @@ class TestContextTests extends BaseTestsSuite {
   }
 
   testAsync("IO.shift via Timer") { ec =>
-    implicit val cs = ec.contextShift[IO]
+    implicit val cs: ContextShift[IO] = ec.ioContextShift
 
     val f = IO.shift.flatMap(_ => IO(1 + 1)).unsafeToFuture()
     assert(f.value === None)

From c11d299fd883890d82a89d365f0430bac554cc97 Mon Sep 17 00:00:00 2001
From: Travis Brown <travisrobertbrown@gmail.com>
Date: Wed, 29 Jan 2020 12:43:32 +0000
Subject: [PATCH 2/5] Add type annotations

---
 .../scala/cats/effect/DeferredJVMTests.scala  |  4 +--
 .../test/scala/cats/effect/IOJVMTests.scala   |  6 ++---
 .../test/scala/cats/effect/MVarJVMTests.scala |  4 +--
 .../scala/cats/effect/SemaphoreJVMTests.scala |  4 +--
 .../effect/ConcurrentCancelableFTests.scala   |  2 +-
 .../effect/ConcurrentContinualTests.scala     |  6 ++---
 .../scala/cats/effect/IOCancelableTests.scala |  8 +++---
 .../src/test/scala/cats/effect/IOTests.scala  | 26 +++++++++----------
 .../test/scala/cats/effect/MemoizeTests.scala | 10 +++----
 9 files changed, 35 insertions(+), 35 deletions(-)

diff --git a/laws/jvm/src/test/scala/cats/effect/DeferredJVMTests.scala b/laws/jvm/src/test/scala/cats/effect/DeferredJVMTests.scala
index bd153365a4..05513c1bf7 100644
--- a/laws/jvm/src/test/scala/cats/effect/DeferredJVMTests.scala
+++ b/laws/jvm/src/test/scala/cats/effect/DeferredJVMTests.scala
@@ -33,14 +33,14 @@ class DeferredJVMParallelism4Tests extends BaseDeferredJVMTests(4)
 abstract class BaseDeferredJVMTests(parallelism: Int) extends AnyFunSuite with Matchers with BeforeAndAfter {
   var service: ExecutorService = _
 
-  implicit val context = new ExecutionContext {
+  implicit val context: ExecutionContext = new ExecutionContext {
     def execute(runnable: Runnable): Unit =
       service.execute(runnable)
     def reportFailure(cause: Throwable): Unit =
       cause.printStackTrace()
   }
 
-  implicit val cs = IO.contextShift(context)
+  implicit val cs: ContextShift[IO] = IO.contextShift(context)
   implicit val timer: Timer[IO] = IO.timer(context)
 
   before {
diff --git a/laws/jvm/src/test/scala/cats/effect/IOJVMTests.scala b/laws/jvm/src/test/scala/cats/effect/IOJVMTests.scala
index fede4c1d45..2ded4120aa 100644
--- a/laws/jvm/src/test/scala/cats/effect/IOJVMTests.scala
+++ b/laws/jvm/src/test/scala/cats/effect/IOJVMTests.scala
@@ -94,7 +94,7 @@ class IOJVMTests extends AnyFunSuite with Matchers {
 
   test("parMap2 concurrently") {
     import scala.concurrent.ExecutionContext.Implicits.global
-    implicit val cs = IO.contextShift(global)
+    implicit val cs: ContextShift[IO] = IO.contextShift(global)
 
     val io1 = IO.shift *> IO(1)
     val io2 = IO.shift *> IO(2)
@@ -107,7 +107,7 @@ class IOJVMTests extends AnyFunSuite with Matchers {
 
   test("long synchronous loops that are forked are cancelable") {
     val thread = new AtomicReference[Thread](null)
-    implicit val ec = new ExecutionContext {
+    implicit val ec: ExecutionContext = new ExecutionContext {
       def execute(runnable: Runnable): Unit = {
         val th = new Thread(runnable)
         if (!thread.compareAndSet(null, th))
@@ -122,7 +122,7 @@ class IOJVMTests extends AnyFunSuite with Matchers {
       val latch = new java.util.concurrent.CountDownLatch(1)
       def loop(): IO[Int] = IO.suspend(loop())
 
-      implicit val ctx = IO.contextShift(ec)
+      implicit val ctx: ContextShift[IO] = IO.contextShift(ec)
       val task = IO.shift *> IO(latch.countDown()) *> loop()
       val c = task.unsafeRunCancelable {
         case Left(e) => e.printStackTrace()
diff --git a/laws/jvm/src/test/scala/cats/effect/MVarJVMTests.scala b/laws/jvm/src/test/scala/cats/effect/MVarJVMTests.scala
index fba124c406..1a2c80afd5 100644
--- a/laws/jvm/src/test/scala/cats/effect/MVarJVMTests.scala
+++ b/laws/jvm/src/test/scala/cats/effect/MVarJVMTests.scala
@@ -101,14 +101,14 @@ class MVarFullJVMParallelism4Tests extends BaseMVarJVMTests(4) {
 abstract class BaseMVarJVMTests(parallelism: Int) extends AnyFunSuite with Matchers with BeforeAndAfter {
   var service: ExecutorService = _
 
-  implicit val context = new ExecutionContext {
+  implicit val context: ExecutionContext = new ExecutionContext {
     def execute(runnable: Runnable): Unit =
       service.execute(runnable)
     def reportFailure(cause: Throwable): Unit =
       cause.printStackTrace()
   }
 
-  implicit val cs = IO.contextShift(context)
+  implicit val cs: ContextShift[IO] = IO.contextShift(context)
   implicit val timer: Timer[IO] = IO.timer(context)
 
   before {
diff --git a/laws/jvm/src/test/scala/cats/effect/SemaphoreJVMTests.scala b/laws/jvm/src/test/scala/cats/effect/SemaphoreJVMTests.scala
index 2197241df8..c8b8054f53 100644
--- a/laws/jvm/src/test/scala/cats/effect/SemaphoreJVMTests.scala
+++ b/laws/jvm/src/test/scala/cats/effect/SemaphoreJVMTests.scala
@@ -35,14 +35,14 @@ class SemaphoreJVMParallelism4Tests extends BaseSemaphoreJVMTests(4)
 abstract class BaseSemaphoreJVMTests(parallelism: Int) extends AnyFunSuite with Matchers with BeforeAndAfter {
   var service: ExecutorService = _
 
-  implicit val context = new ExecutionContext {
+  implicit val context: ExecutionContext = new ExecutionContext {
     def execute(runnable: Runnable): Unit =
       service.execute(runnable)
     def reportFailure(cause: Throwable): Unit =
       cause.printStackTrace()
   }
 
-  implicit val cs = IO.contextShift(context)
+  implicit val cs: ContextShift[IO] = IO.contextShift(context)
   implicit val timer: Timer[IO] = IO.timer(context)
 
   before {
diff --git a/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala b/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala
index 0dfbdfaeee..e45931a850 100644
--- a/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ConcurrentCancelableFTests.scala
@@ -115,7 +115,7 @@ class ConcurrentCancelableFTests extends BaseTestsSuite {
     import scala.concurrent.duration._
 
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     var effect = 0
     val task = Concurrent.cancelableF[IO, Unit] { cb =>
diff --git a/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala b/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala
index 829149e519..14c22a8999 100644
--- a/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ConcurrentContinualTests.scala
@@ -25,7 +25,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
   testAsync("Concurrent.continual allows interruption of its input") { implicit ec =>
     import scala.concurrent.duration._
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val task = Ref[IO].of(false).flatMap { canceled =>
       (IO.never: IO[Unit])
@@ -43,7 +43,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
   testAsync("Concurrent.continual backpressures on finalizers") { implicit ec =>
     import scala.concurrent.duration._
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val task = Ref[IO].of(false).flatMap { canceled =>
       (IO.never: IO[Unit])
@@ -96,7 +96,7 @@ class ConcurrentContinualTests extends BaseTestsSuite {
   testAsync("Concurrent.continual respects the continual guarantee") { implicit ec =>
     import scala.concurrent.duration._
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val task = Ref[IO].of(false).flatMap { completed =>
       IO.unit
diff --git a/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala b/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
index 59a2fe795e..92aaba947a 100644
--- a/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
@@ -89,7 +89,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("bracket back-pressures on the finalizer") { ec =>
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val p1 = Promise[Unit]()
     val io = IO.unit.bracket(_ => IO.never: IO[Unit]) { _ =>
@@ -116,7 +116,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("CancelUtils.cancelAll") { ec =>
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val token1 = IO.sleep(1.seconds)
     val token2 = IO.sleep(2.seconds)
@@ -142,7 +142,7 @@ class IOCancelableTests extends BaseTestsSuite {
   }
 
   testAsync("nested brackets are sequenced") { ec =>
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
     val atom = new AtomicInteger(0)
 
     val io =
@@ -226,7 +226,7 @@ class IOCancelableTests extends BaseTestsSuite {
 
   // regression test for https://github.com/typelevel/cats-effect/issues/487
   testAsync("bracket can be canceled while failing to acquire") { ec =>
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val io = (IO.sleep(2.second) *> IO.raiseError[Unit](new Exception()))
       .bracket(_ => IO.unit)(_ => IO.unit)
diff --git a/laws/shared/src/test/scala/cats/effect/IOTests.scala b/laws/shared/src/test/scala/cats/effect/IOTests.scala
index a81dc29a9f..2f5b8bcb73 100644
--- a/laws/shared/src/test/scala/cats/effect/IOTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOTests.scala
@@ -66,7 +66,7 @@ class IOTests extends BaseTestsSuite {
   )
 
   checkAllAsync("IO(Effect defaults)", implicit ec => {
-    implicit val ioEffect = IOTests.ioEffectDefaults
+    implicit val ioEffect: Effect[IO] = IOTests.ioEffectDefaults
     EffectTests[IO].effect[Int, Int, Int]
   })
 
@@ -74,7 +74,7 @@ class IOTests extends BaseTestsSuite {
     "IO(ConcurrentEffect defaults)",
     implicit ec => {
       implicit val cs: ContextShift[IO] = ec.ioContextShift
-      implicit val ioConcurrent = IOTests.ioConcurrentEffectDefaults(ec)
+      implicit val ioConcurrent: ConcurrentEffect[IO] = IOTests.ioConcurrentEffectDefaults(ec)
       ConcurrentEffectTests[IO].concurrentEffect[Int, Int, Int]
     }
   )
@@ -221,7 +221,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("IO.sleep") { ec =>
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val io = IO.sleep(10.seconds) *> IO(1 + 1)
     val f = io.unsafeToFuture()
@@ -453,7 +453,7 @@ class IOTests extends BaseTestsSuite {
   testAsync("sync.to[IO] is stack-safe") { implicit ec =>
     // Override default generator to only generate
     // synchronous instances that are stack-safe
-    implicit val arbIO = Arbitrary(genSyncIO[Int].map(_.toIO))
+    implicit val arbIO: Arbitrary[IO[Int]] = Arbitrary(genSyncIO[Int].map(_.toIO))
 
     check { (io: IO[Int]) =>
       repeatedTransformLoop(10000, io) <-> io
@@ -681,7 +681,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("IO.timeout can mirror the source") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     check { (ioa: IO[Int]) =>
       ioa.timeout(1.day) <-> ioa
@@ -690,7 +690,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("IO.timeout can end in timeout") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val task = for {
       p <- Deferred[IO, Unit]
@@ -760,7 +760,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("bracket does not evaluate use on cancel") { implicit ec =>
     implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     var use = false
     var release = false
@@ -1086,7 +1086,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("cancel should wait for already started finalizers on success") { implicit ec =>
     implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val fa = for {
       pa <- Deferred[IO, Unit]
@@ -1106,7 +1106,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("cancel should wait for already started finalizers on failure") { implicit ec =>
     implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val dummy = new RuntimeException("dummy")
 
@@ -1128,7 +1128,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("cancel should wait for already started use finalizers") { implicit ec =>
     implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val fa = for {
       pa <- Deferred[IO, Unit]
@@ -1152,7 +1152,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("second cancel should wait for use finalizers") { implicit ec =>
     implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val fa = for {
       pa <- Deferred[IO, Unit]
@@ -1176,7 +1176,7 @@ class IOTests extends BaseTestsSuite {
 
   testAsync("second cancel during acquire should wait for it and finalizers to complete") { implicit ec =>
     implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val fa = for {
       pa <- Deferred[IO, Unit]
@@ -1202,7 +1202,7 @@ class IOTests extends BaseTestsSuite {
   testAsync("second cancel during acquire should wait for it and finalizers to complete (non-terminating)") {
     implicit ec =>
       implicit val contextShift: ContextShift[IO] = ec.ioContextShift
-      implicit val timer = ec.timer[IO]
+      implicit val timer: Timer[IO] = ec.timer[IO]
 
       val fa = for {
         pa <- Deferred[IO, Unit]
diff --git a/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala b/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
index db05a3b023..4b81ed718f 100644
--- a/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
@@ -96,7 +96,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Memoized effects can be canceled when there are no other active subscribers (1)") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val prog = for {
       completed <- Ref[IO].of(false)
@@ -116,7 +116,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Memoized effects can be canceled when there are no other active subscribers (2)") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val prog = for {
       completed <- Ref[IO].of(false)
@@ -139,7 +139,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Memoized effects can be canceled when there are no other active subscribers (3)") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val prog = for {
       completed <- Ref[IO].of(false)
@@ -162,7 +162,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Running a memoized effect after it was previously canceled reruns it") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val prog = for {
       started <- Ref[IO].of(0)
@@ -184,7 +184,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Attempting to cancel a memoized effect with active subscribers is a no-op") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    implicit val timer = ec.timer[IO]
+    implicit val timer: Timer[IO] = ec.timer[IO]
 
     val prog = for {
       condition <- Deferred[IO, Unit]

From 461fe53fef861b8e7612868e91135c1cb7b42416 Mon Sep 17 00:00:00 2001
From: Travis Brown <travisrobertbrown@gmail.com>
Date: Wed, 29 Jan 2020 14:54:37 +0000
Subject: [PATCH 3/5] Add parentheses for Dotty

---
 .../src/test/scala/cats/effect/IOTests.scala       |  2 +-
 .../src/test/scala/cats/effect/MemoizeTests.scala  |  2 +-
 .../src/test/scala/cats/effect/ResourceTests.scala | 14 +++++++-------
 .../src/test/scala/cats/effect/SyncIOTests.scala   |  2 +-
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/laws/shared/src/test/scala/cats/effect/IOTests.scala b/laws/shared/src/test/scala/cats/effect/IOTests.scala
index 2f5b8bcb73..ce343a539d 100644
--- a/laws/shared/src/test/scala/cats/effect/IOTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOTests.scala
@@ -93,7 +93,7 @@ class IOTests extends BaseTestsSuite {
   }
 
   testAsync("throw in register is fail") { implicit ec =>
-    check { e: Throwable =>
+    check { (e: Throwable) =>
       IO.async[Unit](_ => throw e) <-> IO.raiseError(e)
     }
   }
diff --git a/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala b/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
index 4b81ed718f..5a39b70ffb 100644
--- a/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/MemoizeTests.scala
@@ -89,7 +89,7 @@ class MemoizeTests extends BaseTestsSuite {
 
   testAsync("Concurrent.memoize and then flatten is identity") { implicit ec =>
     implicit val cs: ContextShift[IO] = ec.ioContextShift
-    check { fa: IO[Int] =>
+    check { (fa: IO[Int]) =>
       Concurrent.memoize(fa).flatten <-> fa
     }
   }
diff --git a/laws/shared/src/test/scala/cats/effect/ResourceTests.scala b/laws/shared/src/test/scala/cats/effect/ResourceTests.scala
index cb56bb5c87..db70237f1f 100644
--- a/laws/shared/src/test/scala/cats/effect/ResourceTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/ResourceTests.scala
@@ -41,7 +41,7 @@ class ResourceTests extends BaseTestsSuite {
   }
 
   test("releases resources in reverse order of acquisition") {
-    check { as: List[(Int, Either[Throwable, Unit])] =>
+    check { (as: List[(Int, Either[Throwable, Unit])]) =>
       var released: List[Int] = Nil
       val r = as.traverse {
         case (a, e) =>
@@ -91,7 +91,7 @@ class ResourceTests extends BaseTestsSuite {
   }
 
   testAsync("liftF") { implicit ec =>
-    check { fa: IO[String] =>
+    check { (fa: IO[String]) =>
       Resource.liftF(fa).use(IO.pure) <-> fa
     }
   }
@@ -175,7 +175,7 @@ class ResourceTests extends BaseTestsSuite {
   }
 
   testAsync("mapK") { implicit ec =>
-    check { fa: Kleisli[IO, Int, Int] =>
+    check { (fa: Kleisli[IO, Int, Int]) =>
       val runWithTwo = new ~>[Kleisli[IO, Int, *], IO] {
         override def apply[A](fa: Kleisli[IO, Int, A]): IO[A] = fa(2)
       }
@@ -219,7 +219,7 @@ class ResourceTests extends BaseTestsSuite {
   }
 
   testAsync("allocated produces the same value as the resource") { implicit ec =>
-    check { resource: Resource[IO, Int] =>
+    check { (resource: Resource[IO, Int]) =>
       val a0 = Resource(resource.allocated).use(IO.pure).attempt
       val a1 = resource.use(IO.pure).attempt
 
@@ -240,7 +240,7 @@ class ResourceTests extends BaseTestsSuite {
       _ <- IO(released.get() shouldBe true)
     } yield ()
 
-    prog.unsafeRunSync
+    prog.unsafeRunSync()
   }
 
   test("allocate does not release until close is invoked on mapK'd Resources") {
@@ -252,7 +252,7 @@ class ResourceTests extends BaseTestsSuite {
     val takeAnInteger = new ~>[IO, Kleisli[IO, Int, *]] {
       override def apply[A](fa: IO[A]): Kleisli[IO, Int, A] = Kleisli.liftF(fa)
     }
-    val plusOne = Kleisli { i: Int =>
+    val plusOne = Kleisli { (i: Int) =>
       IO { i + 1 }
     }
     val plusOneResource = Resource.liftF(plusOne)
@@ -268,7 +268,7 @@ class ResourceTests extends BaseTestsSuite {
       _ <- IO(released.get() shouldBe true)
     } yield ()
 
-    prog.unsafeRunSync
+    prog.unsafeRunSync()
   }
 
   test("safe attempt suspended resource") {
diff --git a/laws/shared/src/test/scala/cats/effect/SyncIOTests.scala b/laws/shared/src/test/scala/cats/effect/SyncIOTests.scala
index 8b4d48be37..984687ac2d 100644
--- a/laws/shared/src/test/scala/cats/effect/SyncIOTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/SyncIOTests.scala
@@ -91,7 +91,7 @@ class SyncIOTests extends BaseTestsSuite {
       }
     }
 
-    val value = loop.unsafeRunSync
+    val value = loop.unsafeRunSync()
     value shouldEqual count
   }
 

From a16399efa4ffe858892ebfcb06a614247755651c Mon Sep 17 00:00:00 2001
From: Travis Brown <travisrobertbrown@gmail.com>
Date: Wed, 29 Jan 2020 14:56:53 +0000
Subject: [PATCH 4/5] Explicitly discard values

---
 laws/shared/src/test/scala/cats/effect/FiberTests.scala      | 2 +-
 laws/shared/src/test/scala/cats/effect/IOAsyncTests.scala    | 4 ++--
 .../src/test/scala/cats/effect/IOCancelableTests.scala       | 5 ++++-
 laws/shared/src/test/scala/cats/effect/IOTests.scala         | 2 +-
 4 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/laws/shared/src/test/scala/cats/effect/FiberTests.scala b/laws/shared/src/test/scala/cats/effect/FiberTests.scala
index 18158488e4..118c6fad3d 100644
--- a/laws/shared/src/test/scala/cats/effect/FiberTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/FiberTests.scala
@@ -104,7 +104,7 @@ class FiberTests extends BaseTestsSuite {
         _ <- IO.fromFuture(IO.pure(latch1.future))
         _ <- IO.fromFuture(IO.pure(latch2.future))
         _ <- fiber1.map2(fiber2)(_ + _).cancel
-      } yield fiber2.join
+      } yield { fiber2.join; () }
 
     f.unsafeToFuture()
     ec.tick()
diff --git a/laws/shared/src/test/scala/cats/effect/IOAsyncTests.scala b/laws/shared/src/test/scala/cats/effect/IOAsyncTests.scala
index d71a6c2985..d394c9a10e 100644
--- a/laws/shared/src/test/scala/cats/effect/IOAsyncTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOAsyncTests.scala
@@ -42,8 +42,8 @@ class IOAsyncTests extends AsyncFunSuite with Matchers {
     effect.future.onComplete(attempt.success)
 
     val io = source.runAsync {
-      case Right(a) => IO(effect.success(a))
-      case Left(e)  => IO(effect.failure(e))
+      case Right(a) => IO { effect.success(a); () }
+      case Left(e)  => IO { effect.failure(e); () }
     }
 
     for (_ <- io.toIO.unsafeToFuture(); v <- attempt.future) yield {
diff --git a/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala b/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
index 92aaba947a..93d8828e40 100644
--- a/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOCancelableTests.scala
@@ -93,7 +93,7 @@ class IOCancelableTests extends BaseTestsSuite {
 
     val p1 = Promise[Unit]()
     val io = IO.unit.bracket(_ => IO.never: IO[Unit]) { _ =>
-      IO.sleep(3.seconds) *> IO(p1.success(()))
+      IO.sleep(3.seconds) *> IO(p1.success(())).void
     }
 
     val p2 = Promise[Unit]()
@@ -151,16 +151,19 @@ class IOCancelableTests extends BaseTestsSuite {
           IO(3).bracket(_ => IO.never: IO[Unit]) { x3 =>
             IO.sleep(3.seconds) *> IO {
               atom.compareAndSet(0, x3) shouldBe true
+              ()
             }
           }
         } { x2 =>
           IO.sleep(2.seconds) *> IO {
             atom.compareAndSet(3, x2) shouldBe true
+            ()
           }
         }
       } { x1 =>
         IO.sleep(1.second) *> IO {
           atom.compareAndSet(2, x1) shouldBe true
+          ()
         }
       }
 
diff --git a/laws/shared/src/test/scala/cats/effect/IOTests.scala b/laws/shared/src/test/scala/cats/effect/IOTests.scala
index ce343a539d..798e03c534 100644
--- a/laws/shared/src/test/scala/cats/effect/IOTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOTests.scala
@@ -316,7 +316,7 @@ class IOTests extends BaseTestsSuite {
       val io1 = IO.fromFuture(IO(Future { effect = f(effect, a) }))
       val io2 = IO.fromFuture(IO(Future { effect = g(effect, a) }))
 
-      io2.flatMap(_ => io1).flatMap(_ => io2) <-> IO(g(f(g(a, a), a), a))
+      io2.flatMap(_ => io1).flatMap(_ => io2) <-> IO(g(f(g(a, a), a), a)).void
     }
   }
 

From 2c7ee8e2a30a13e802da2c8bfa07f141780e1c26 Mon Sep 17 00:00:00 2001
From: Travis Brown <travisrobertbrown@gmail.com>
Date: Wed, 29 Jan 2020 15:42:45 +0000
Subject: [PATCH 5/5] Fix import in Scala.js test

---
 .../test/scala/cats/effect/internals/IOContextShiftTests.scala  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala b/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala
index e5078ad43e..41947681b5 100644
--- a/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala
+++ b/laws/js/src/test/scala/cats/effect/internals/IOContextShiftTests.scala
@@ -16,7 +16,7 @@
 
 package cats.effect.internals
 
-import cats.effect.{BaseTestsSuite, IO}
+import cats.effect.{BaseTestsSuite, ContextShift, IO}
 import scala.util.Success
 
 class IOContextShiftTests extends BaseTestsSuite {