Visual Studio is over 43 million lines of code, there are over 30 teams working on different pieces, with roughly 700 developers checking-in code to 11 different virtual build labs that are then integrated on a rotating schedule producing over 100 different builds of the product daily.
In addition we have interdependencies with SQL and MSDN. When we ship
an official release like a Beta or RTM (release to market) we lock down
and are code complete several months before the actual release date to
allow for a final test pass, to stabilize and hit stress goals, then
get the best bits to fulfillment for mass production of media. Before
code complete there is a long list of exit criteria for the product
that must be met, ensuring all key features and scenarios meet
expectations. We have customer bug exit criteria to ensure high
priority issues are fixed.
We've had a very interesting challenge scaling
development and testing techniques up to a product of that size. It
seems like most methodologies ("You just write unit tests for
everything and then you have no bugs") I hear about are really intended
for about 5 person teams. If you had a unit test for every 10 lines of
code, that's 4 million unit tests. That's would be a lot of unit tests
to run before a single check-in.
Fonte : http://blogs.msdn.com/jmstall/archive/2005/08/23/How_big_is_Vs.aspx