The VsTestRunner plugin allows you to run unit test via vstest.console.exe and it fails the job (or marks it as unstable) when a test fails, but it does not publish the test results like a junit job does. If you want to know how many tests have run, or why something failed, you have to check the console output.

Using the vstest.console.exe of VS2013 and /Logger:trx you get a trx file that the mstest plugin, which has a "Publish mstest test result report" post build task, cannot interprete: see JENKINS-19360.