Backport #5225 test in 2.x

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/databind/ser/jdk/UUIDSerializationTest.java

@@ -14,6 +14,9 @@
 
 public class UUIDSerializationTest extends DatabindTestUtil
 {
+    private final static String nullUUIDStr = "00000000-0000-0000-0000-000000000000";
+    private final static UUID nullUUID = UUID.fromString(nullUUIDStr);
+
     static class UUIDWrapperVanilla {
         public UUID uuid;
 
@@ -88,4 +91,18 @@ public void testShapeOverrides() throws Exception
         assertEquals("{\"uuid\":\"AAAAAAAAAAAAAAAAAAAAAA==\"}",
                 m.writeValueAsString(new UUIDWrapperVanilla(nullUUID)));
     }
+
+    // [databind#5225]: problem with tree conversion
+    @Test
+    public void testTreeConversion() throws Exception
+    {
+        // First, reported issue
+        JsonNode node = MAPPER.valueToTree(nullUUID);
+        assertEquals(nullUUIDStr, node.asText());
+
+        // and then a variations
+        Object ob = MAPPER.convertValue(nullUUID, Object.class);
+        assertEquals(String.class, ob.getClass());
+    }
+
 }