David Mortenson details how Facebook maintained efficiency while increasing the number of engineers by reducing the n00b time sink, keeping development fast and avoiding unintended consequences.
David Mortenson is an Engineering Manager at Facebook with more than 13 years of experience in software development. Prior to joining Facebook, David was Director of Development at Microsoft for the .Net Framework core platform. David holds a Masters in Computer Science from the University of Washington.
Software is changing the world; QCon aims to empower software development by facilitating the spread of knowledge and innovation in the enterprise software development community; to achieve this, QCon is organized as a practitioner-driven conference designed for people influencing innovation in their teams: team leads, architects, project managers, engineering directors.
Many of the issues they had with their tests (e.g. flakiness and slow test runs) were clearly results of relying primarily integrated tests  instead of unit tests. For example running 10k unit tests  should only take some tens of seconds, with the average unit test taking just a millisecond or so to run. But the slide at 35:10 clearly shows that Facebook's tests are awfully slow - well over a second each.
 www.infoq.com/presentations/integration-tests-scam www.jbrains.ca/permalink/integrated-tests-are-a...
 pragprog.com/magazines/2012-01/unit-tests-are-f... agileinaflash.blogspot.fi/2009/02/first.html