add testcase

src/test/java/com/alibaba/druid/bvt/utils/DruidWebUtilsTest.java

@@ -0,0 +1,32 @@
+package com.alibaba.druid.bvt.utils;
+
+import junit.framework.TestCase;
+
+import org.junit.Assert;
+import org.springframework.mock.web.MockServletContext;
+
+import com.alibaba.druid.util.DruidWebUtils;
+
+public class DruidWebUtilsTest extends TestCase {
+
+    public void test_getContextPath_2_5() throws Exception {
+        new DruidWebUtils(); //
+
+        MockServletContext context = new MockServletContext() {
+
+            public int getMajorVersion() {
+                return 2;
+            }
+
+            public int getMinorVersion() {
+                return 4;
+            }
+
+            public String getContextPath() {
+                throw new NoSuchMethodError();
+            }
+        };
+
+        Assert.assertNull(DruidWebUtils.getContextPath(context));
+    }
+}