diff --git a/tests/src/test/scala/cats/tests/EitherTests.scala b/tests/src/test/scala/cats/tests/EitherTests.scala
index c7f9f86303..47f1c7db2f 100644
--- a/tests/src/test/scala/cats/tests/EitherTests.scala
+++ b/tests/src/test/scala/cats/tests/EitherTests.scala
@@ -10,7 +10,7 @@ class EitherTests extends CatsSuite {
   implicit val iso = CartesianTests.Isomorphisms.invariant[Either[Int, ?]]
 
   checkAll("Either[String, Int]", GroupLaws[Either[String, Int]].monoid)
-  checkAll("Semigroup[Either[String, Int]]", SerializableTests.serializable(Semigroup[Either[String, Int]]))
+  checkAll("Monoid[Either[String, Int]]", SerializableTests.serializable(Monoid[Either[String, Int]]))
 
   checkAll("Either[Int, Int]", CartesianTests[Either[Int, ?]].cartesian[Int, Int, Int])
   checkAll("Cartesian[Either[Int, ?]]", SerializableTests.serializable(Cartesian[Either[Int, ?]]))
diff --git a/tests/src/test/scala/cats/tests/IdTTests.scala b/tests/src/test/scala/cats/tests/IdTTests.scala
index 2c05aa80fb..e362eec7a1 100644
--- a/tests/src/test/scala/cats/tests/IdTTests.scala
+++ b/tests/src/test/scala/cats/tests/IdTTests.scala
@@ -1,7 +1,6 @@
 package cats
 package tests
 
-import cats.{Foldable, Functor, Monad, NonEmptyTraverse, Traverse}
 import cats.data.{IdT, NonEmptyList}
 import cats.kernel.laws.OrderLaws
 import cats.laws.discipline._
diff --git a/tests/src/test/scala/cats/tests/WriterTTests.scala b/tests/src/test/scala/cats/tests/WriterTTests.scala
index 50274a9503..41aee6457d 100644
--- a/tests/src/test/scala/cats/tests/WriterTTests.scala
+++ b/tests/src/test/scala/cats/tests/WriterTTests.scala
@@ -336,6 +336,7 @@ class WriterTTests extends CatsSuite {
 
     Monoid[WriterT[ListWrapper, Int, Int]]
     checkAll("WriterT[ListWrapper, Int, Int]", kernel.laws.GroupLaws[WriterT[ListWrapper, Int, Int]].monoid)
+    checkAll("Monoid[WriterT[ListWrapper, Int, Int]]", SerializableTests.serializable(Monoid[WriterT[ListWrapper, Int, Int]]))
 
     Monoid[Writer[Int, Int]]
     checkAll("Writer[Int, Int]", kernel.laws.GroupLaws[Writer[Int, Int]].monoid)
@@ -347,6 +348,7 @@ class WriterTTests extends CatsSuite {
 
     Semigroup[WriterT[ListWrapper, Int, Int]]
     checkAll("WriterT[ListWrapper, Int, Int]", kernel.laws.GroupLaws[WriterT[ListWrapper, Int, Int]].semigroup)
+    checkAll("Semigroup[WriterT[ListWrapper, Int, Int]]", SerializableTests.serializable(Semigroup[WriterT[ListWrapper, Int, Int]]))
 
     Semigroup[Writer[Int, Int]]
     checkAll("Writer[Int, Int]", kernel.laws.GroupLaws[Writer[Int, Int]].semigroup)