Add tests related to #4409 (#4411)

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/databind/deser/enums/EnumDeserDupName4409Test.java

@@ -0,0 +1,41 @@
+package com.fasterxml.jackson.databind.deser.enums;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+// for [databind#4409
+public class EnumDeserDupName4409Test extends DatabindTestUtil
+{
+    // for [databind#4409
+    enum ColorMode4409Snake {
+        // Will become "rgb"
+        RGB,
+        // Will become "rgba"
+        RGBa,
+        // Will become "rgba" as well unless overriden, so:
+        @JsonProperty("RGBA")
+        RGBA
+    }
+
+    private final ObjectMapper MAPPER = jsonMapperBuilder()
+            .propertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE)
+            .build();
+
+    // for [databind#4409
+    @Test
+    public void dupNameConflict4409() throws Exception
+    {
+        assertEquals(ColorMode4409Snake.RGBa,
+                MAPPER.readValue(q("RGBa"), ColorMode4409Snake.class));
+
+        assertEquals(q("RGBA"),
+                MAPPER.writeValueAsString(ColorMode4409Snake.RGBA));
+    }
+}

src/test/java/com/fasterxml/jackson/databind/introspect/TestNamingStrategyStd.java

@@ -238,6 +238,9 @@ public void setUtcZone(String utcZone) {
                 {"uId", "u_id" },
                 // [databind#2267]
                 {"xCoordinate", "x_coordinate" },
+                // [databind#4409]
+                {"RGBA", "rgba"},
+                {"RGBa", "rgba"},
     });
 
     final static List<Object[]> UPPER_SNAKE_CASE_NAME_TRANSLATIONS = Arrays.asList(new Object[][] {