Female engineer Tina Huang is suing Twitter for gender discrimination . Claims she was overlooked for promotion in favour of male colleagues . Says the Silicon Valley firm has no formal procedure for promotions . And alleges there was a 'shoulder tap ' process that favoured men . Comment: Comes as Silicon Valley rocked by two other high profile lawsuits .
Female engineer Tina Huang is suing Twitter for gender discrimination . Claims she was overlooked for promotion in favour of male colleagues . Says the Silicon Valley firm has no formal procedure for promotions . And alleges there was a 'shoulder tap ' process that favoured men . Twitter says it is committed to diversity and that she was treated fairly . Comes as Silicon Valley rocked by two other high profile lawsuits .