Add a test for #3484 (commented out for now)

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/databind/interop/UntypedObjectWithDupsTest.java

@@ -0,0 +1,71 @@
+package com.fasterxml.jackson.databind.interop;
+
+import java.util.Map;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.StreamReadCapability;
+import com.fasterxml.jackson.core.util.JacksonFeatureSet;
+import com.fasterxml.jackson.core.util.JsonParserDelegate;
+import com.fasterxml.jackson.databind.*;
+
+// Mostly for XML but can be tested via JSON with some trickery
+public class UntypedObjectWithDupsTest extends BaseMapTest
+{
+    private final ObjectMapper JSON_MAPPER = newJsonMapper();
+
+    // For [dataformat-xml#???]
+    public void testDocWithDupsAsUntyped() throws Exception
+    {
+        _readWriteDocAs(Object.class);
+    }
+
+    // For [dataformat-xml#498] / [databind#3484]
+    public void testDocWithDupsAsMap() throws Exception
+    {
+//        _readWriteDocAs(Map.class);
+    }
+
+    private <T> void _readWriteDocAs(Class<T> cls) throws Exception
+    {
+        final String doc = a2q(
+                "{'hello': 'world',\n"
+                + "'lists' : 1,\n"
+                + "'lists' : 2,\n"
+                + "'lists' : {\n"
+                + "  'inner' : 'internal',\n"
+                + "  'time' : 123\n"
+                + "},\n"
+                + "'lists' : 3,\n"
+                + "'single' : 'one'\n"
+                + "}");
+        // This is where need some trickery
+        T value;
+        try (JsonParser p = new WithDupsParser(JSON_MAPPER.createParser(doc))) {
+            value = JSON_MAPPER.readValue(p, cls);
+        }
+
+        String json = JSON_MAPPER.writeValueAsString(value);
+        assertEquals(a2q(
+"{'hello':'world','lists':[1,2,"
++"{'inner':'internal','time':123},3],'single':'one'}"),
+                json);
+    }
+
+    /**
+     * Helper class to fake "DUPLICATE_PROPERTIES" on JSON parser
+     * (which usually does not expose this).
+     */
+    static class WithDupsParser extends JsonParserDelegate
+    {
+        public WithDupsParser(JsonParser p) {
+            super(p);
+        }
+
+        @Override
+        public JacksonFeatureSet<StreamReadCapability> getReadCapabilities() {
+            JacksonFeatureSet<StreamReadCapability> caps = super.getReadCapabilities();
+            caps = caps.with(StreamReadCapability.DUPLICATE_PROPERTIES);
+            return caps;
+        }
+    }
+}