Portable Appliance testing or PAT testing is the process of examining an electrical appliance to ensure it is safe for use. Most defects are visually identifiable but others can only be found with rigourous testing.
 A portable appliance is an item that can be moved and usually unplugged from a power supply. It can be something as small as a kettle or as big as a free standing fridge.

Where a landlord provides an electrical appliance as part of a tenancy, the law expects the appliance will be maintained in a safe condition that will not cause harm to the tenant. PAT testing is always best practice for landlords.