1 files changed, 39 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/UnknownElementIndexTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/UnknownElementIndexTest.kt
new file mode 100644
index 00000000..3fb4bc04
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/UnknownElementIndexTest.kt
@@ -0,0 +1,39 @@
+package kotlinx.serialization
+
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.CompositeDecoder.Companion.UNKNOWN_NAME
+import kotlinx.serialization.encoding.*
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.modules.*
+import kotlin.test.Test
+import kotlin.test.assertFailsWith
+
+class UnknownElementIndexTest {
+    enum class Choices { A, B, C }
+
+    @Serializable
+    data class Holder(val c: Choices)
+
+    class MalformedReader : AbstractDecoder() {
+        override val serializersModule: SerializersModule = EmptySerializersModule()
+
+        override fun decodeElementIndex(descriptor: SerialDescriptor): Int {
+            return UNKNOWN_NAME
+        }
+    }
+
+    @Test
+    fun testCompilerComplainsAboutIncorrectIndex() {
+        assertFailsWith(SerializationException::class) {
+            MalformedReader().decodeSerializableValue(Holder.serializer())
+        }
+    }
+
+    @Test
+    fun testErrorMessage() {
+        val message = "kotlinx.serialization.UnknownElementIndexTest.Choices does not contain element with name 'D'"
+        assertFailsWith(SerializationException::class, message) {
+            Json.decodeFromString(Holder.serializer(), """{"c":"D"}""")
+        }
+    }
+}