; How Google Tests Software - Part Two | Google Operating System News

Tuesday, 26 July 2011

How Google Tests Software - Part Two

How Google Tests Software - Part Two

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.

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