Wanting to upgrade the department to a later version of SQL Server from a mixture of SQL Server 2000, 2003, 2005, 2008R2 and 2012 databases, I led a team to purchase, install and configure a brand new SQL Server 2016 environment.
Using the automated testing process that I had just implemented, we were able to discover issues before we went into production, such as the correct implementation of the ANSI-92 unordered data-sets in SQL Server. We also discovered through the testing process that some queries performed slower than before, so we were able to investigate and rewrite these queries.
By the time we were ready to go-live, we were confident that very few issues remained, and we were pleased that the actual go-live downtime was just a period of minutes, with no significant issues detected over the coming weeks.