diff --git a/jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/UpgradeResponseAdapterTest.java b/jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/UpgradeResponseAdapterTest.java
new file mode 100644
index 00000000000..69a9418cfbc
--- /dev/null
+++ b/jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/UpgradeResponseAdapterTest.java
@@ -0,0 +1,64 @@
+//
+//  ========================================================================
+//  Copyright (c) 2019 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.websocket.common;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * Unit tests for class {@link UpgradeResponseAdapter}.
+ *
+ * @see UpgradeResponseAdapter
+ */
+public class UpgradeResponseAdapterTest
+{
+
+    @Test
+    public void testAddHeader()
+    {
+        UpgradeResponseAdapter upgradeResponseAdapter = new UpgradeResponseAdapter();
+
+        assertNull(upgradeResponseAdapter.getHeader(""));
+
+        upgradeResponseAdapter.addHeader("", "");
+
+        assertEquals(0, upgradeResponseAdapter.getStatusCode());
+        assertFalse(upgradeResponseAdapter.isSuccess());
+        assertNull(upgradeResponseAdapter.getStatusReason());
+        assertEquals(0, upgradeResponseAdapter.getStatusCode());
+        assertFalse(upgradeResponseAdapter.isSuccess());
+        assertNull(upgradeResponseAdapter.getStatusReason());
+        assertEquals("", upgradeResponseAdapter.getHeader(""));
+
+        upgradeResponseAdapter.addHeader("a", "b");
+
+        assertEquals(0, upgradeResponseAdapter.getStatusCode());
+        assertFalse(upgradeResponseAdapter.isSuccess());
+        assertNull(upgradeResponseAdapter.getStatusReason());
+        assertEquals(0, upgradeResponseAdapter.getStatusCode());
+        assertFalse(upgradeResponseAdapter.isSuccess());
+        assertNull(upgradeResponseAdapter.getStatusReason());
+        assertEquals("", upgradeResponseAdapter.getHeader(""));
+        assertEquals("b", upgradeResponseAdapter.getHeader("a"));
+    }
+
+}