It appears to be an excellent overview of modern software testing techniques. Besides that, it contains a sufficient introduction to Python and Flask.
For beginners:
It teaches the basics of software testing. Unit, integration and end-to-end tests are covered. The author guides students through a whole creation of a simple server application. Moreover, It introduces the audience to many good practices.
For experienced:
It might be a good enough starting point to Python and Flask for a developer with some understanding of OOP and prior experience in backend development.