The hwsim code here can only compile with a very specific kernel
version, but is shipped with current kernels so you just need to enable
it in your kernel instead.
The tests directory and its subdirectories contain a set of configuration
files that can be used to exercise various mac80211, hostapd, and
wpa_supplicant features. The test.txt file in each test directory describes
the particular test and includes the commands needed to run the test.
This new netdev is created by hwsim, not mac80211, and as such, it is
available all the time (i.e., can be UP before starting mac80211 netdevs)
and it will receive all frames regardless of the channel etc.
mac80211_hwsim is a Linux kernel module that can be used to simulate
arbitrary number of IEEE 802.11 radios for mac80211 on a single
device. It can be used to test most of the mac80211 functionality and
user space tools (e.g., hostapd and wpa_supplicant) in a way that
matches very closely with the normal case of using real WLAN
hardware. From the mac80211 view point, mac80211_hwsim is yet another
hardware driver, i.e., no changes to mac80211 are needed to use this
testing tool.
