In some industries, the law is direct and proactive whereas in others it is more reactive. For example, regulations state that gas appliances in workplaces or let accommodation have to be annually tested, whereas electrical appliance testing is, at present, a little more vague and tends to focus on 'duty of care'.
Rather than it being compulsory to have appliances tested, it is the responsibility of each company to fulfil it's duty of care. If there was a situation whereby a company had failed to ensure electrical appliances were safe and that led to injury or fatality then there would be severe penalties for failing to ensure safety.
In plain English, what this means is that although companies aren't forced to have electrical equipment regularly tested, there are high negative impacts if failure to do so results in injury or death. Therefore, 'best practice' is to ensure that companies pro-actively engage in a programme of electrical equipment inspection and testing.