following are web-links for Hadoop certification practice test.
http://www.vskills.in/practice/startPracticeTest/Big-Data-and-Apache-Hadoop-Mock-Test
http://www.tutorialspoint.com/hadoop/hadoop_online_test.htm
http://searchdatamanagement.techtarget.com/quiz/Quiz-Test-your-understanding-of-the-Hadoop-ecosystem
http://my-classes.com/lesson/hadoop-practice-exam-free-sample/
http://www.edureka.co/blog/questions-answers-about-cloudera-certified-developer-for-hadoop-ccdh/
http://www.hub4tech.com/cloudera-certified-developer-hadoop-test-exam