Test automation is an oxymoron. One can’t really automate tests. Developers can automate checks, which increases the quality of the testing, because testers needn’t concern themselves with mind-numbing double checking and verification. The closest thing to automating tests would be generative testing or model-based testing.
Throughout the developer testing book, the phrase “test automation” is used a bit sloppily to describe the act of authoring functional integration, system, or end-to-end tests.