zmk/app/tests/keytoggle/behavior_keymap.dtsi

#include <dt-bindings/zmk/keys.h>
#include <behaviors.dtsi>
#include <dt-bindings/zmk/kscan_mock.h>

/ {
    keymap {
        compatible = "zmk,keymap";

        default_layer {
            bindings = <
                &kt B &none
                &none &none
            >;
        };
    };
};