Google是如何做测试的？

PART I
This is the first in a series of posts on this topic.

The one question I get more than any other is "How does Google test?" It's been explained in bits and pieces on this blog but the explanation is due an update. The Google testing strategy has never changed but the tactical ways we execute it has evolved as the company has evolved. We're now a search, apps, ads, mobile, operating system, and so on and so forth company. Each of these Focus Areas (as we call them) have to do things that make sense for their problem domain. As we add new FAs and grow the existing ones, our testing has to expand and improve. What I am documenting in this series of posts is a combination of what we are doing today and the direction we are trending toward in the foreseeable future.

Let's begin with organizational structure and it's one that might surprise you. There isn't an actual testing organization at Google. Test exists within a Focus Area called Engineering Productivity. Eng Prod owns any number of horizontal and vertical engineering disciplines, Test is the biggest. In a nutshell, Eng Prod is made of:

1. A product team that produces internal and open source productivity tools that are consumed by all walks of engineers across the company. We build and maintain code analyzers, IDEs, test case management systems, automated testing tools, build systems, source control systems, code review schedulers, bug databases... The idea is to make the tools that make engineers more productive. Tools are a very large part of the strategic goal of prevention over detection.

2. A services team that provides expertise to Google product teams on a wide array of topics including tools, documentation, testing, release management, training and so forth. Our expertise covers reliability, security, internationalization, etc., as well as product-specific functional issues that Google product teams might face. Every other FA has access to Eng Prod expertise.

3. Embedded engineers that are effectively loaned out to Google product teams on an as-needed basis. Some of these engineers might sit with the same product teams for years, others cycle through teams wherever they are needed most. Google encourages all its engineers to change product teams often to stay fresh, engaged and objective. Testers are no different but the cadence of changing teams is left to the individual. I have testers on Chrome that have been there for several years and others who join for 18 months and cycle off. Keeping a healthy balance between product knowledge and fresh eyes is something a test manager has to pay close attention to.

So this means that testers report to Eng Prod managers but identify themselves with a product team, like Search, Gmail or Chrome. Organizationally they are part of both teams. They sit with the product teams, participate in their planning, go to lunch with them, share in ship bonuses and get treated like full members of the team. The benefit of the separate reporting structure is that it provides a forum for testers to share information. Good testing ideas migrate easily within Eng Prod giving all testers, no matter their product ties, access to the best technology within the company.

This separation of project and reporting structures has its challenges. By far the biggest is that testers are an external resource. Product teams can't place too big a bet on them and must keep their quality house in order. Yes, that's right: at Google it's the product teams that own quality, not testers. Every developer is expected to do their own testing. The job of the tester is to make sure they have the automation infrastructure and enabling processes that support this self reliance. Testers enable developers to test.

What I like about this strategy is that it puts developers and testers on equal footing. It makes us true partners in quality and puts the biggest quality burden where it belongs: on the developers who are responsible for getting the product right. Another side effect is that it allows us a many-to-one dev-to-test ratio. Developers outnumber testers. The better they are at testing the more they outnumber us. Product teams should be proud of a high ratio!

Ok, now we're all friends here right? You see the hole in this strategy I am sure. It's big enough to drive a bug through. Developers can't test! Well, who am I to deny that? No amount of corporate kool-aid could get me to deny it, especially coming off my GTAC talk last year where I pretty much made a game of developer vs. tester (spoiler alert: the tester wins).

Google's answer is to split the role. We solve this problem by having two types of testing roles at Google to solve two very different testing problems. In my next post, I'll talk about these roles and how we split the testing problem into two parts.

PART II

By James Whittaker

In order for the “you build it, you break it” motto to be real, there are roles beyond the traditional developer that are necessary. Specifically, engineering roles that enable developers to do testing efficiently and effectively have to exist. At Google we have created roles in which some engineers are responsible for making others more productive. These engineers often identify themselves as testers but their actual mission is one of productivity. They exist to make developers more productive and quality is a large part of that productivity. Here's a summary of those roles:

The SWE or Software Engineer is the traditional developer role. SWEs write functional code that ships to users. They create design documentation, design data structures and overall architecture and spend the vast majority of their time writing and reviewing code. SWEs write a lot of test code including test driven design, unit tests and, as we explain in future posts, participate in the construction of small, medium and large tests. SWEs own quality for everything they touch whether they wrote it, fixed it or modified it.

The SET or Software Engineer in Test is also a developer role except their focus is on testability. They review designs and look closely at code quality and risk. They refactor code to make it more testable. SETs write unit testing frameworks and automation. They are a partner in the SWE code base but are more concerned with increasing quality and test coverage than adding new features or increasing performance.

The TE or Test Engineer is the exact reverse of the SET. It is a a role that puts testing first and development second. Many Google TEs spend a good deal of their time writing code in the form of automation scripts and code that drives usage scenarios and even mimics a user. They also organize the testing work of SWEs and SETs, interpret test results and drive test execution, particular in the late stages of a project as the push toward release intensifies. TEs are product experts, quality advisers and analyzers of risk.

From a quality standpoint, SWEs own features and the quality of those features in isolation. They are responsible for fault tolerant designs, failure recovery, TDD, unit tests and in working with the SET to write tests that exercise the code for their feature.

SETs are developers that provide testing features. A framework that can isolate newly developed code by simulating its dependencies with stubs, mocks and fakes and submit queues for managing code check-ins. In other words, SETs write code that allows SWEs to test their features. Much of the actual testing is performed by the SWEs, SETs are there to ensure that features are testable and that the SWEs are actively involved in writing test cases.

Clearly SETs primary focus is on the developer. Individual feature quality is the target and enabling developers to easily test the code they write is the primary focus of the SET. This development focus leaves one large hole which I am sure is already evident to the reader: what about the user?

User focused testing is the job of the Google TE. Assuming that the SWEs and SETs performed module and feature level testing adequately, the next task is to understand how well this collection of executable code and data works together to satisfy the needs of the user. TEs act as a double-check on the diligence of the developers. Any obvious bugs are an indication that early cycle developer testing was inadequate or sloppy. When such bugs are rare, TEs can turn to their primary task of ensuring that the software runs common user scenarios, is performant and secure, is internationalized and so forth. TEs perform a lot of testing and test coordination tasks among TEs, contract testers, crowd sourced testers, dog fooders, beta users, early adopters. They communicate among all parties the risks inherent in the basic design, feature complexity and failure avoidance methods. Once TEs get engaged, there is no end to their mission.

Ok, now that the roles are better understood, I'll dig into more details on how we choreograph the work items among them. Until next time...thanks for your interest.

PART III

By James Whittaker

Lots of questions in the comments to the last two posts. I am not ignoring them. Hopefully many of them will be answered here and in following posts. I am just getting started on this topic.

At Google, quality is not equal to test. Yes I am sure that is true elsewhere too. “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.

However, this is neither as simple nor as accurate as it sounds. While it is true that quality cannot be tested in, it is equally evident that without testing it is impossible to develop anything of quality. How does one decide if what you built is high quality without testing it?

The simple solution to this conundrum is to stop treating development and test as separate disciplines. Testing and development go hand in hand. Code a little and test what you built. Then code some more and test some more. Better yet, plan the tests while you code or even before. Test isn’t a separate practice, it’s part and parcel of the development process itself. Quality is not equal to test; it is achieved by putting development and testing into a blender and mixing them until one is indistinguishable from the other.

At Google this is exactly our goal: to merge development and testing so that you cannot do one without the other. Build a little and then test it. Build some more and test some more. The key here is who is doing the testing. Since the number of actual dedicated testers at Google is so disproportionately low, the only possible answer has to be the developer. Who better to do all that testing than the people doing the actual coding? Who better to find the bug than the person who wrote it? Who is more incentivized to avoid writing the bug in the first place? The reason Google can get by with so few dedicated testers is because developers own quality. In fact, teams that insist on having a large testing presence are generally assumed to be doing something wrong. Having too large a test team is a very strong sign that the code/test mix is out of balance. Adding more testers is not going to solve anything.

This means that quality is more an act of prevention than it is detection. Quality is a development issue, not a testing issue. 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 testers necessary to ensure the absence of recall-class bugs. At Google, testing is aimed at determining how well this prevention method is working. TEs are constantly on the lookout for evidence that the SWE-SET combination of bug writers/preventers are screwed toward the latter and TEs raise alarms when that process seems out of whack.

Manifestations of this blending of development and testing are all over the place from code review notes asking ‘where are your tests?’ to posters in the bathrooms reminding developers about best testing practices, our infamous Testing On The Toilet guides. Testing must be an unavoidable aspect of development and the marriage of development and testing is where quality is achieved. SWEs are testers, SETs are testers and TEs are testers.

If your organization is also doing this blending, please share your successes and challenges with the rest of us. If not, then here is a change you can help your organization make: get developers fully vested in the quality equation. You know the old saying that chickens are happy to contribute to a bacon and egg breakfast but the pig is fully committed? Well, it's true...go oink at one of your developer and see if they oink back. If they start clucking, you have a problem.