Add failing test for #4697 (#4711)

src/test/java/com/fasterxml/jackson/databind/tofix/JsonUnwrappedInconsistentSerialization4697Test.java

@@ -0,0 +1,58 @@
+package com.fasterxml.jackson.databind.tofix;
+
+import com.fasterxml.jackson.annotation.JsonUnwrapped;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+import com.fasterxml.jackson.databind.testutil.failure.JacksonTestFailureExpected;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+// [databind#4697] Inconsistent Serialization with Jackson’s @JsonUnwrapped Annotation
+//                 Using Shared vs. New ObjectMapper Instances #4697
+public class JsonUnwrappedInconsistentSerialization4697Test
+        extends DatabindTestUtil
+{
+    public static class First {
+        @JsonUnwrapped(prefix = "")
+        public Third thrid = new Third();
+    }
+
+    public static class Second {
+        @JsonUnwrapped(prefix = "fromSecond")
+        public Third thrid = new Third();
+    }
+
+    public static class Third {
+        @JsonUnwrapped(prefix = "fromThird")
+        public Common common = new Common();
+
+        public Third() {
+            this.common.a = "a";
+            this.common.b = "b";
+        }
+    }
+
+    public static class Common {
+        public String a;
+        public String b;
+        public Common() {}
+    }
+
+    @JacksonTestFailureExpected
+    @Test
+    public void testInconsistentSer() throws Exception {
+        First first = new First();
+        Second second = new Second();
+
+        ObjectMapper firstMapper = newJsonMapper();
+        ObjectMapper secondMapper = newJsonMapper();
+
+        firstMapper.writeValueAsString(first);
+        assertEquals(
+                firstMapper.writeValueAsString(second),
+                secondMapper.writeValueAsString(second));
+    }
+}