I am getting following error in my script

does that mean i am missing any jar file which i need to include in liabrary or something else.
Looks like you need to include the jmeter library in your project.
Include all jars from the following JMeter folders:
into your project classpath as well as Selenium libraries.
By the way, are you aware of existing WebDriver Sampler which integrates JMeter and Selenium so you won't have to recompile your JUnit code in case of any changes on Selenium side of things.