Test Automation is the use of software to control the execution of tests and the comparison of actual outcomes with predicted outcomes.

Wikipedia, Test Automation [Wikipedia]

Testing automation tools enable developers and/or testers to easily automate the entire process of testing in software development.

E. H. Kim, J. C. Na and S. M. Ryoo, "Implementing an Effective Test Automation Framework," 2009 33rd Annual IEEE International Computer Software and Applications Conference, Seattle, WA, 2009, pp. 534-538. [IEEE Explore]

Test automation is a term used in software testing and some other kinds of IT related testing or quality assurance. It means that there is no human input required to generate a test. Different kinds of test automation help businesses to pursue goals like software testing with fewer resources, or in more efficient ways.

Website: Techopedia, online: https://www.techopedia.com/definition/17789/test-automation, last visit 03.09.2019 [Techopedia]