import kotlinx.serialization.*
import kotlinx.serialization.json.*
import kotlinx.serialization.modules.SerializersModule
import kotlinx.serialization.modules.polymorphic

interface Test {
    val prop1 : String
    val prop2 : String
}

@Serializable
data class TestImpl(
    override val prop1 : String,
    override val prop2 : String
) : Test

fun main() {
    val encoder = Json {
        serializersModule = SerializersModule {
            polymorphic(Test::class) {
                subclass(TestImpl::class, TestImpl.serializer())
                default { TestImpl.serializer() }
            }
        }
    }

    val data : Test = TestImpl("blah", "blah")
    println(encoder.encodeToString(data))
}