Add unit tests

proxy/src/main/java/com/velocitypowered/proxy/connection/client/HandshakeSessionHandler.java

@@ -138,8 +138,15 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
     }
   }
 
-  private String cleanVhost(String hostname) {
-    // Clean out any anything after any zero byte
+  /**
+   * Cleans the specified virtual host hostname.
+   *
+   * @param hostname the host name to clean
+   * @return the cleaned hostname
+   */
+  static String cleanVhost(String hostname) {
+    // Clean out any anything after any zero bytes (this includes BungeeCord forwarding and the
+    // legacy Forge handshake indicator).
     String cleaned = hostname;
     int zeroIdx = cleaned.indexOf('\0');
     if (zeroIdx > -1) {

proxy/src/test/java/com/velocitypowered/proxy/connection/client/HandshakeSessionHandlerTest.java

@@ -0,0 +1,31 @@
+package com.velocitypowered.proxy.connection.client;
+
+import static com.velocitypowered.proxy.connection.client.HandshakeSessionHandler.cleanVhost;
+import static com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants;
+import org.junit.jupiter.api.Test;
+
+class HandshakeSessionHandlerTest {
+
+  @Test
+  void cleanVhostHandlesGoodHostname() {
+    assertEquals("localhost", cleanVhost("localhost"));
+  }
+
+  @Test
+  void cleanVhostHandlesTrailingOctet() {
+    assertEquals("localhost", cleanVhost("localhost."));
+  }
+
+  @Test
+  void cleanVhostHandlesForge() {
+    assertEquals("localhost", cleanVhost("localhost" + HANDSHAKE_HOSTNAME_TOKEN));
+  }
+
+  @Test
+  void cleanVhostHandlesOctetsAndForge() {
+    assertEquals("localhost", cleanVhost("localhost." + HANDSHAKE_HOSTNAME_TOKEN));
+  }
+}