Microsoft.Data.Tools.UnitTest.dll is a database unit test component in SQL Server Data Tools (SSDT). SSDT transforms database development by introducing a ubiquitous, declarative model that spans all the phases of database development inside Visual Studio. You can use SSDT Transact-SQL design capabilities to build, debug, maintain, and refactor databases. You can work with a database project, or directly with a connected database instance on or off-premise. You can use SQL Server unit tests to establish a baseline state for your database and then to verify any subsequent changes that you make to database objects. SSDT team's blog - https://blogs.msdn.microsoft.com/ssdt/ SQL Server Data Tools page - https://docs.microsoft.com/sql/ssdt/sql-server-data-tools More details about SQL Server unit Tests - https://docs.microsoft.com/sql/ssdt/verifying-database-code-by-using-sql-server-unit-tests