added test cases for polymorphic serialization

Author: rasros

README.md

@@ -1,6 +1,6 @@
 <p align="center">
   <a href="https://eignex.com/">
-    <img src="https://raw.githubusercontent.com/Eignex/.github/refs/heads/main/profile/banner.svg" style="max-width: 100%; width: 22em" />
+    <img src="https://raw.githubusercontent.com/Eignex/.github/refs/heads/main/profile/banner.svg" style="max-width: 100%; width: 22em"  alt="Eignex">
   </a>
 </p>
 
@@ -85,7 +85,9 @@ payloads for Kotlin classes by moving structural metadata into a compact header.
 * VarInts: Int/Long fields can be optimized using @VarUInt or @VarInt (ZigZag)
   annotations.
 * Full Graph Support: Handles nested objects, lists, maps, and polymorphism
-  recursively.
+  recursively. While this is supported it will not produce as compact 
+  representations as flat structures that can pack all metadata into the same 
+  header.
 
 ### Field layout
 

src/test/kotlin/com/eignex/kencode/PackedFormatTest.kt

@@ -147,7 +147,27 @@ class PackedFormatTest {
                 ),
                 nestedLists = listOf(listOf(listOf(1, 2), listOf(3))),
                 optionalDeepMap = mapOf(42 to null)
-            )
+            ),
+
+            DeepBreadth(
+                branchA = Level1(true, Level2("data-a", listOf(listOf(1)))),
+                branchB = Level1(false, null),
+                branchC = Level1(true, Level2("data-c", emptyList())),
+                rootValue = 999
+            ),
+
+            PolymorphicContainer(
+                main = PolymorphicBase.Action("Login", 1),
+                history = listOf(
+                    PolymorphicBase.Notification("Welcome!", false),
+                    PolymorphicBase.Heartbeat,
+                    PolymorphicBase.Action("Update", 2),
+                    PolymorphicBase.Notification("Hello", true),
+                )
+            ),
+
+            PolymorphicBase.Heartbeat,
+            PolymorphicBase.Action("Standalone", 0)
         )
 
         testData.forEach { value ->

src/test/kotlin/com/eignex/kencode/TestClasses.kt

@@ -229,3 +229,19 @@ data class MultiLevelCollections(
     val nestedLists: List<List<List<Int>>>,
     val optionalDeepMap: Map<Int, Map<String, Boolean>?>?
 )
+
+@Serializable
+sealed class PolymorphicBase {
+    @Serializable
+    data class Action(val name: String, val priority: Int) : PolymorphicBase()
+    @Serializable
+    data class Notification(val message: String, val silent: Boolean) : PolymorphicBase()
+    @Serializable
+    object Heartbeat : PolymorphicBase()
+}
+
+@Serializable
+data class PolymorphicContainer(
+    val main: PolymorphicBase,
+    val history: List<PolymorphicBase>
+)