Add rate limiting filter IP test

Author: gvaguirres

src/test/java/org/example/filter/RateLimitingFilterIpTest.java

@@ -0,0 +1,47 @@
+package org.example.filter;
+
+import org.example.http.HttpResponseBuilder;
+import org.example.httpparser.HttpRequest;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.example.filter.RateLimitingFilter.resolveClientIp;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+class RateLimitingFilterIpTest {
+
+    @Mock HttpRequest request;
+    @Mock HttpResponseBuilder response;
+
+    @Test
+    void shouldUseXForwarded_WhenPresent(){
+
+        Map<String, String> headers = new HashMap<>();
+        headers.put("X-Forwarded-For", "203.0.113.195");
+
+        when(request.getHeaders()).thenReturn(headers);
+        when(request.getAttribute("clientIp")).thenReturn("127.0.0.1");
+
+        String finalIp = resolveClientIp(request, response);
+
+        assertEquals("203.0.113.195", finalIp);
+    }
+
+    @Test
+    void shouldFallbackToAttribute_WhenXForwardedForIsNotPresent(){
+
+        when(request.getAttribute("clientIp")).thenReturn(Map.of());
+        when(request.getAttribute("clientIp")).thenReturn("10.0.0.5");
+
+        String finalIp = resolveClientIp(request, response);
+
+        assertEquals("10.0.0.5", finalIp);
+    }
+}