Breakpoints not hit in specflow

I'm writing a test case using SpecFlow in C#. When I set appropriate breakpoints and run the test cases using debugger, all the breakpoints are not hit. When I hover over them, a tip displaying "The breakpoint will not be hit. No symbols have been loaded for the document" is shown. Now, how do I debug the testcases that I have written?

PS: I'm using VS2015