The unit testing bootstrap loads and initializes WooCommerce, this
loads a bunch of code files that can't then be hacked in the test hooks.
A workaround is provided in this commit for the case of hacking
static methods. A new StaticWrapper class is created that allows
defining mock methods after the code file has been loaded.
This is applied to all classes from a fixed list in the bootstrap,
before WooCommerce is initialized. The list should be kept up to date
with the list of classes that require such workaround.
Nestor Soriano