I have a windows service and want to automate the test cases

Kindly refer the below links, Hope this will solve your problem.

https://msdn.microsoft.com/en-us/library/jj159335.aspx

http://ambracode.com/index/show/344133

https://www.youtube.com/watch?v=_L79cLTzNcE

http://www.softwaretestingmentor.com/automation/writing-your-first-test-case-in-selenium-webdriver/

http://www.codeproject.com/Articles/843207/Automated-Testing-Of-Web-Pages-Using-Selenium-Web

http://www.faichi.com/blog/automated-selenium-testing-framework-using-testng-webdriver

Let me know for any thing more....

If your problem solved means kindly Accept my answer