Added test for invalid server responses

src/test/java/org/littleshoot/proxy/test/ServerErrorTest.java

@@ -0,0 +1,94 @@
+package org.littleshoot.proxy.test;
+
+import org.junit.After;
+import org.junit.Test;
+import org.littleshoot.proxy.HttpProxyServer;
+import org.littleshoot.proxy.impl.DefaultHttpProxyServer;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+import static org.junit.Assert.assertEquals;
+
+public class ServerErrorTest {
+    private HttpProxyServer proxyServer;
+
+    @Test
+    public void testInvalidServerResponse() throws IOException {
+        proxyServer = DefaultHttpProxyServer.bootstrap()
+                .withPort(0)
+                .start();
+
+        // we have to create our own socket here, since any proper http server (jetty, mockserver, etc.) won't allow us to
+        // send invalid responses.
+        try (ServerSocket socket = createServerWithBadResponse()) {
+            org.apache.http.HttpResponse response = HttpClientUtil.performHttpGet("http://localhost:" + socket.getLocalPort(), proxyServer);
+
+            assertEquals("Expected to receive a 502 Bad Gateway after server responded with invalid response", 502, response.getStatusLine().getStatusCode());
+        }
+    }
+
+    @After
+    public void tearDown() {
+        if (proxyServer != null) {
+            proxyServer.abort();
+        }
+    }
+
+    /**
+     * Creates a ServerSocket that will read an HTTP request and response with an invalid response.
+     * NOTE: the ServerSocket must be closed after the response is consumed.
+     */
+    private static ServerSocket createServerWithBadResponse() {
+        final ServerSocket serverSocket;
+        try {
+            serverSocket = new ServerSocket(0);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        Runnable server = new Runnable() {
+            @Override
+            public void run() {
+                try {
+                    Socket socket = serverSocket.accept();
+
+                    try (PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
+                         BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()))) {
+                        while (!in.readLine().isEmpty()) {
+                            // read the request up to the double-CRLF
+                        }
+
+                        // write a a response with an invalid HTTP version
+                        out.write("HTTP/1.12312312312312411231231231 200 OK\r\n" +
+                                "Connection: close\r\n" +
+                                "Content-Length: 0\r\n" +
+                                "\r\n");
+                        out.flush();
+                    }
+                } catch (IOException e) {
+                    throw new RuntimeException(e);
+                }
+            }
+        };
+
+        // start the server in a separate thread
+        Thread serverThread = new Thread(server);
+        serverThread.setDaemon(true);
+        serverThread.start();
+
+        // wait for the server to start
+        try {
+            Thread.sleep(500);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+
+        return serverSocket;
+    }
+
+}