Add test

Author: k163377

src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/github/GitHub618.kt

@@ -0,0 +1,30 @@
+package com.fasterxml.jackson.module.kotlin.test.github
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.SerializerProvider
+import com.fasterxml.jackson.databind.annotation.JsonSerialize
+import com.fasterxml.jackson.databind.ser.std.StdSerializer
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class GitHub618 {
+    @JsonSerialize(using = V.Serializer::class)
+    @JvmInline
+    value class V(val value: String) {
+        class Serializer : StdSerializer<V>(V::class.java) {
+            override fun serialize(p0: V, p1: JsonGenerator, p2: SerializerProvider) {
+                p1.writeString(p0.toString())
+            }
+        }
+    }
+
+    data class D(val v: V?)
+
+    @Test
+    fun test() {
+        val mapper = jacksonObjectMapper()
+        // expected: {"v":null}, but NullPointerException thrown
+        assertEquals("""{"v":null}""", mapper.writeValueAsString(D(null)))
+    }
+}