Add a failing test for #2725

src/test/java/com/fasterxml/jackson/failing/EnumAsMapKey2725Test.java

@@ -0,0 +1,56 @@
+package com.fasterxml.jackson.failing;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class EnumAsMapKey2725Test extends BaseMapTest
+{
+    // [databind#2725]
+    enum TestEnum2725 {
+        FOO(1);
+
+        private final int i;
+
+        TestEnum2725(final int i) {
+            this.i = i;
+        }
+
+        @JsonValue
+        public int getI() {
+            return i;
+        }
+
+        @JsonCreator
+        public static TestEnum2725 getByIntegerId(final Integer id) {
+            return id == FOO.i ? FOO : null;
+        }
+
+        @JsonCreator
+        public static TestEnum2725 getByStringId(final String id) {
+            return Integer.parseInt(id) == FOO.i ? FOO : null;
+        }
+    }
+
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    // [databind#2725]
+    public void testEnumAsMapKey2725() throws Exception
+    {
+        final Map<TestEnum2725, String> input = new HashMap<>();
+        input.put(TestEnum2725.FOO, "Hello");
+
+        final String json = MAPPER.writeValueAsString(input);
+
+        final Map<TestEnum2725, String> output = MAPPER.readValue(json,
+                new TypeReference<Map<TestEnum2725, String>>() { });
+
+        assertNotNull(output);
+        assertEquals(1, output.size());
+    }
+}