Add failing test for #2816

src/test/java/com/fasterxml/jackson/failing/DeepNestingWithUntyped2816Test.java

@@ -0,0 +1,46 @@
+package com.fasterxml.jackson.failing;
+
+import java.util.List;
+import java.util.Map;
+
+import com.fasterxml.jackson.databind.*;
+
+// [databind#2816]
+public class DeepNestingWithUntyped2816Test extends BaseMapTest
+{
+    // 2000 passes, 3000 fails
+    private final static int TOO_DEEP_NESTING = 4000;
+
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    public void testWithArray() throws Exception
+    {
+        final String doc = _nestedDoc(TOO_DEEP_NESTING, "[ ", "] ");
+        Object ob = MAPPER.readValue(doc, Object.class);
+        assertTrue(ob instanceof List<?>);
+    }
+
+    public void testWithObject() throws Exception
+    {
+        final String doc = "{"+_nestedDoc(TOO_DEEP_NESTING, "\"x\":{", "} ") + "}";
+        Object ob = MAPPER.readValue(doc, Object.class);
+        assertTrue(ob instanceof Map<?,?>);
+    }
+
+    private String _nestedDoc(int nesting, String open, String close) {
+        StringBuilder sb = new StringBuilder(nesting * (open.length() + close.length()));
+        for (int i = 0; i < nesting; ++i) {
+            sb.append(open);
+            if ((i & 31) == 0) {
+                sb.append("\n");
+            }
+        }
+        for (int i = 0; i < nesting; ++i) {
+            sb.append(close);
+            if ((i & 31) == 0) {
+                sb.append("\n");
+            }
+        }
+        return sb.toString();
+    }
+}