Added tests for DateParser

Signed-off-by: Michael Hausegger <hausegger.michael@googlemail.com>

jetty-http/src/test/java/org/eclipse/jetty/http/DateParserTest.java

@@ -0,0 +1,45 @@
+//
+//  ========================================================================
+//  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.http;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Unit tests for class {@link DateParser}.
+ *
+ * @see DateParser
+ */
+public class DateParserTest
+{
+
+    @Test
+    public void testParseDateWithNonDateString()
+    {
+        assertEquals((-1L), DateParser.parseDate("3%~"));
+    }
+
+    @Test
+    public void testParseDateWithNonDateStringEndingWithGMT()
+    {
+        assertEquals((-1L), DateParser.parseDate("3%~ GMT"));
+    }
+
+}