Added IpFilterTest class with unit test verifying IpFilter allows whi… (#76)

* Added IpFilterTest class with unit test verifying IpFilter allows whitelisted IPs.

* Fix IpFilterTest to verify response interaction instead of mock state

* Added unit test for blocking IP that is not in the whitelist, results in 403 Forbidden response.

Fixed HttpResponse construtors to always initialize headers and body to prevent NPE when filters call setHeader or setBody.

* Update IpFilter whitelist allow test to use real HttpResponse

* Assert expected status code in IpFilter whitelist allow test

Author: SandraNelj

src/main/java/org/juv25d/http/HttpResponse.java

@@ -15,14 +15,16 @@ public class HttpResponse {
     private byte[] body;
 
     public HttpResponse(){
+        this.statusCode = 200;
+        this.statusText = "OK";
         this.headers = new LinkedHashMap<>();
         this.body = new byte[0];
     }
 
     public HttpResponse(int statusCode, String statusText, Map<String, String> headers, byte[] body) {
         this.statusCode = statusCode;
         this.statusText = statusText;
-        this.headers = new LinkedHashMap<>(headers);
+        this.headers = headers != null ? new LinkedHashMap<>(headers) : new LinkedHashMap<>();
         this.body = body != null ? body.clone() : new byte[0];
     }
 

src/test/java/org/juv25d/filter/IpFilterTest.java

@@ -0,0 +1,45 @@
+package org.juv25d.filter;
+import org.junit.jupiter.api.Test;
+import org.juv25d.http.HttpRequest;
+import org.juv25d.http.HttpResponse;
+import java.io.IOException;
+import java.util.Set;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.*;
+
+class IpFilterTest {
+
+    @Test
+    void whitelist_allowsIp() throws IOException {
+        IpFilter filter = new IpFilter(Set.of("127.0.0.1"), null);
+
+        HttpRequest req = mock(HttpRequest.class);
+        when(req.remoteIp()).thenReturn("127.0.0.1");
+
+        HttpResponse res = new HttpResponse();
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(req, res, chain);
+
+        verify(chain).doFilter(req, res);
+        assertEquals(200, res.statusCode());
+    }
+
+    @Test
+    void whitelist_blocksIpNotInList() throws IOException {
+        IpFilter filter = new IpFilter(Set.of("10.0.0.1"), null);
+
+        HttpRequest req = mock(HttpRequest.class);
+        when(req.remoteIp()).thenReturn("127.0.0.1");
+
+        HttpResponse res = new HttpResponse();
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(req, res, chain);
+        verify(chain, never()).doFilter(req, res);
+
+        assertEquals(403, res.statusCode());
+        assertEquals("Forbidden", res.statusText());
+
+    }
+}