Integrating Unit Tests from multiple developers in visual studio2012

We have a situation where multiple developers are developing their respective unit test cases using VS2012 in their local environment. End of the day they need to upload their Unit tests to the same folder in source control (we use GIT). The CI is then supposed to 'build' and 'execute' and all these tests.

My question is how do we integrate these UT's developed by various developers into a single solution, so that it can be built and executed all at the same time.

Its a SQL server project where we are testing various store procedures.

Thanks in advance for any tips.