javascript - Angular data-binding after setting input value with karma -

my question extremely close 1 :

update angular model after setting input value jquery

but, here, input modified val() method of karma runner :

element('#stuff_input').val('thenewvalforstuff'); 

i won't detail test here, irrelevant. guess test fail if binding not maintained.

in production, #stuff_input modified keyboard user, never jquery method of course. don't want use $watch, don't want introduce more complexity production code because :

1) karma not allow keyboard input natively

2) karma event not maintain data-binding val()

any idea of how solve ?

thanks