SDET stands for Software Development Engineer in Test. The term seems to have been made up by Google for developers who are involved in creating efficient testing automation tools (frameworks, libraries) and implementing them – both technical aspects and the practices and approaches. The main distinction from QA Automation Engineers lies in the development of libraries, frameworks, or complete products for testing, as well as educating teams on writing tests, rather than solely focusing on continuous test writing.

Some believe that this term was compromised within Google itself, as SDETs often performed the traditional roles of regular automation engineers. Others consider that in the modern world of DevOps and more complex CD/CI pipelines with advanced technical tools, this term is even more relevant. In the post-Soviet space, the term hasn't been compromised for sure, perhaps because things tend to reach us with a delay. Maybe that's for the better :)