side-effects • You can see WHAT the change was in SCM • You need to know WHY the change was made hence the Bug # (and SCM-/Tracking integration) • Only then you can reliably fix the side-effect without breaking • previous bug fixes • other features Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
is still in the topic • She‘s able to directly fix the issues without having to re-think the situation when a bug report comes in a few days (or weeks) later • Other devs know of the problem and don‘t check out broken versions that causes them problems • Enables automated testing Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
in trunk/master • Features • Bug fixes • Reintegrate into release-branch only if 100% sure • that it‘s tested • you‘re confident in stability Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
are distracting • WTF WTF WTF • „Look at that! Can you tell me what he meant by this?“ • Reviewer needs too much time to get in the code • Unproductive and time consuming • Reviewer could mob developer • „You‘re not working with our guidelines“ • „But *Everyone* knows that {very special way of doing things here}“ Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
shoulder“ reviews • Developer seeks reviewer in person • Developer explains to reviewer • Reviewer asks questions and points to possible problems • Developer takes notes • Developer fixes • Developer checks in Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
Usual guess? • x2, or 100% • 50 % initial overhead while the pair syncs up • About 15 % overhead on the long run Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
9.2h / 2 à 4.6 h • Half a day + half an hour • Task: 8h • Alone: x1 à 8h • Alone: 8h / 1 à 8h • One full day Let‘s do the math Single Developer Pair Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
% less defects • Since costs to fix a defect later is higher than instant fixing that alone saves more than pair programming costs • About 20 % less lines of code • Better architecture • Distributed knowledge • Higher motivation • Less distraction Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
learned, all point to the fact that TDD seems to be applicable in various domains and can significantly reduce the defect density of developed software without significant productivity reduction of the development team.“ Source: http://research.microsoft.com/en-us/groups/ese/nagappan_tdd.pdf November 2014 - EKON 18
Full TDD (test first) for everything • 50% less defects - after 2 years • No mention on costs, though • Second link (study from IBM & MS) • Costs: Time only. 15% to 35% more • Gains: Bug ratio went down to 61% (and one product down to 9%!) Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
• Code is only written testable if tests are there upfront • New features within existing code are hard to cover with TDD • Writing tests is not easy and fast to learn • especially when there‘s no TDD culture and mentors around Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
TDD • Start with simple features to get used to it • If you access not-tested infrastructure, wrap it with something mockable that just passes through in production • Write tests for existing code only • when you need to do major refactorings • when you fix a bug and that code is already testable • or almost, with little work Sebastian P.R. Gingter - @PhoenixHawk November 2014 - EKON 18
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