Typeclass serialization tests

src/examples/show.scala

@@ -6,7 +6,7 @@ import magnolia1._
   *
   * Note that this is a more general form of `Show` than is usual, as it permits the return type to be something other than a string.
   */
-trait Show[Out, T] { def show(value: T): Out }
+trait Show[Out, T] extends Serializable { def show(value: T): Out }
 
 trait GenericShow[Out] extends AutoDerivation[[X] =>> Show[Out, X]] {
 

src/test/SerializationTests.scala

@@ -0,0 +1,43 @@
+package magnolia1.tests
+
+import magnolia1.*
+import magnolia1.examples.*
+
+import java.io.*
+class SerializationTests extends munit.FunSuite:
+  import SerializationTests.*
+
+  private def serializeToByteArray(value: Serializable): Array[Byte] =
+    val buffer = new ByteArrayOutputStream()
+    val oos = new ObjectOutputStream(buffer)
+    oos.writeObject(value)
+    buffer.toByteArray
+
+  private def deserializeFromByteArray(encodedValue: Array[Byte]): AnyRef =
+    val ois = new ObjectInputStream(new ByteArrayInputStream(encodedValue))
+    ois.readObject()
+
+  def ensureSerializable[T <: Serializable](value: T): T =
+    deserializeFromByteArray(serializeToByteArray(value)).asInstanceOf[T]
+
+  test("generate serializable type-classes") {
+    ensureSerializable(new Outer().showAddress)
+    ensureSerializable(new Outer().showColor)
+  }
+
+object SerializationTests:
+  sealed trait Entity
+  case class Company(name: String) extends Entity
+  case class Person(name: String, age: Int) extends Entity
+  case class Address(line1: String, occupant: Person)
+
+  sealed trait Color
+  case object Red extends Color
+  case object Green extends Color
+  case object Blue extends Color
+  case object Orange extends Color
+  case object Pink extends Color
+  class Outer:
+    val showAddress: Show[String, Address] = summon[Show[String, Address]]
+    val showColor: Show[String, Color] = summon[Show[String, Color]]
+