feat: make HttpResponse mutable and implement NotFoundPlugin default

src/main/java/org/juv25d/Pipeline.java

@@ -17,6 +17,9 @@ public void addFilter(Filter filter) {
     }
 
     public void setPlugin(Plugin plugin) {
+        if (plugin == null) {
+            throw new IllegalArgumentException("Plugin cannot be null");
+        }
         this.plugin = plugin;
     }
 
@@ -31,4 +34,12 @@ public void init() {
     public void destroy() {
         filters.forEach(Filter::destroy);
     }
+
+    public List<Filter> getFilters() {
+        return filters;
+    }
+
+    public Plugin getPlugin() {
+        return plugin;
+    }
 }

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

@@ -2,37 +2,57 @@
 
 import java.util.*;
 
+/**
+ * Represents an HTTP Response.
+ * Changed to be mutable to allow Filters and Plugins in the Pipeline
+ * to modify status, headers, and body during processing.
+ */
 public class HttpResponse {
 
-    private final int statusCode;
-    private final String statusText;
-    private final Map<String, String> headers;
-    private final byte[] body;
+    private int statusCode;
+    private String statusText;
+    private Map<String, String> headers;
+    private byte[] body;
+
+    public HttpResponse(){}
 
     public HttpResponse(int statusCode, String statusText, Map<String, String> headers, byte[] body) {
-        Objects.requireNonNull(statusText, "statusText must not be null");
-        Objects.requireNonNull(headers, "headers must not be null");
-        Objects.requireNonNull(body, "body must not be null");
         this.statusCode = statusCode;
         this.statusText = statusText;
-        this.headers = Collections.unmodifiableMap(new LinkedHashMap<>(headers));
-        this.body = body.clone();
+        this.headers = new LinkedHashMap<>(headers);
+        this.body = body != null ? body.clone() : new byte[0];
     }
 
-    public int statusCode(){
+    public int statusCode() {
         return statusCode;
     }
 
-    public String statusText(){
+    public void setStatusCode(int statusCode) {
+        this.statusCode = statusCode;
+    }
+
+    public String statusText() {
         return statusText;
     }
 
+    public void setStatusText(String statusText) {
+        Objects.requireNonNull(statusText, "statusText must not be null");
+        this.statusText = statusText;
+    }
+
     public Map<String, String> headers() {
         return headers;
     }
 
-    public byte[] body(){
-        return body.clone();
+    public void setHeader(String name, String value) {
+        headers.put(name, value);
     }
 
+    public byte[] body() {
+        return body != null ? body.clone() : new byte[0];
+    }
+
+    public void setBody(byte[] body) {
+        this.body = body != null ? body.clone() : new byte[0];
+    }
 }

src/main/java/org/juv25d/plugin/NotFoundPlugin.java

@@ -0,0 +1,15 @@
+package org.juv25d.plugin;
+
+import org.juv25d.http.HttpRequest;
+import org.juv25d.http.HttpResponse;
+
+import java.io.IOException;
+
+public class NotFoundPlugin implements Plugin {
+    @Override
+    public void handle(HttpRequest req, HttpResponse res) throws IOException {
+        res.setStatusCode(404);
+        res.setStatusText("Not Found");
+        res.setBody("404 - Resource Not Found".getBytes());
+    }
+}

src/test/java/org/juv25d/PipelineTest.java

@@ -0,0 +1,25 @@
+package org.juv25d;
+
+import org.junit.jupiter.api.Test;
+import org.juv25d.plugin.HelloPlugin;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PipelineTest {
+
+    @Test
+    void throwsExceptionWhenSettingNullPlugin() {
+        Pipeline pipeline = new Pipeline();
+        assertThrows(IllegalArgumentException.class, () -> pipeline.setPlugin(null));
+    }
+
+    @Test
+    void customPluginIsUsed() {
+        Pipeline pipeline = new Pipeline();
+        HelloPlugin hello = new HelloPlugin();
+
+        pipeline.setPlugin(hello);
+
+        assertEquals(hello, pipeline.getPlugin());
+    }
+}

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

@@ -6,6 +6,7 @@
 
 import java.io.IOException;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.Mockito.*;
 
 class LoggingFilterTest {
@@ -42,9 +43,9 @@ void logsHttpMethodAndPath() throws IOException {
             filter.doFilter(req, res, chain);
 
             String output = out.toString();
-            assert output.contains("GET /test");
+            assertTrue(output.contains("GET /test"), "Output should contain logged method and path");
         } finally {
             System.setOut(originalOut);
         }
     }
-}
+}

src/test/java/org/juv25d/plugin/NotFoundPluginTest.java

@@ -0,0 +1,26 @@
+package org.juv25d.plugin;
+
+import org.juv25d.http.HttpRequest;
+import org.juv25d.http.HttpResponse;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class NotFoundPluginTest {
+
+    @Test
+    void sets404StatusAndBody() throws IOException {
+        NotFoundPlugin plugin = new NotFoundPlugin();
+        HttpRequest req = new HttpRequest("GET", "/unknown", null, "HTTP/1.1", Map.of(), new byte[0]);
+        HttpResponse res = new HttpResponse();
+
+        plugin.handle(req, res);
+
+        assertEquals(404, res.statusCode());
+        assertEquals("Not Found", res.statusText());
+        assertArrayEquals("404 - Resource Not Found".getBytes(), res.body());
+    }
+}