As mentioned at the beginning of the chapter, pytest is written from the ground up with customization and flexibility in mind. The plugin mechanism is at the core of the pytest architecture, so much so that many of pytest's built-in features are implemented in terms of internal plugins, such as marks, parametrization, fixtures—nearly everything, even command-line options.
This flexibility has led to an enormous and rich plugin ecosystem. At the time of writing, the number of plugins available is over 500, and that number keeps increasing at an astonishing rate.
