How Google Tests Software

To the extent that we are able to embed testing practice inside development, we have created a process that is hyper-incremental where mistakes can be rolled back if any one increment turns out to be too buggy. We’ve not only prevented a lot of customer issues, we have greatly reduced the number of dedicated testers necessary to ensure the absence

Only those problems, in any of the previous categories, that specifically require human judgment, such as the beauty of a user interface or whether exposing some piece of data constitutes a privacy concern, should remain in the realm of manual testing.

Finally, the mix between automated and manual testing definitely favors the former for all three sizes of tests. If it can be automated and the problem doesn’t require human cleverness and intuition, then it should be automated.

The simple solution to this conundrum is to stop treating development and test as separate disciplines. Testing and development go hand in hand.

The question a small test attempts to answer is, “Does this code do what it is supposed to do?”

For these types of tests, the person who writes the code and understands it best is the one who is most qualified to test it.

Manifestations of this blending of development and testing are inseparable from the Google development mindset, from code review notes asking “where are your tests?” to posters in the bathrooms reminding developers about best-testing practices.

“Quality cannot be tested in” is so cliché it has to be true. From automobiles to software, if it isn’t built right in the first place, then it is never going to be right. Ask any car company that has ever had to do a mass recall how expensive it is to bolt on quality after the fact. Get it right from the beginning or you’ve created a permanent mes

in order to have adequate tests, they had to write two or three lines of unit test code for every line of code under test and that those tests required at least as much maintenance as the functional code itself and had just as much chance of being buggy.