i'm new in Angular, jasmine test

I need to write a jasmine test from this function:

changeAllRooms() {
    const allRoomsFlag = !this.form.value.allRooms;
    (this.rooms || []).forEach((room) => (this.form.controls['rooms'] as FormGroup).controls[room.id]
        .patchValue(allRoomsFlag, {onlySelf: true,
                    emitEvent: false,
                    emitModelToViewChange: true}));
    // this.form.controls['allRooms'].patchValue(allRoomsFlag, {onlySelf: true, emitEvent: false});
}

i'm new in angular