The paperwork you should get from an electrician
Every job produces a document. Here is which one, and what to do with it.
A new circuit or a new board
An Electrical Installation Certificate, with the test readings for every circuit. For a consumer unit change, the council is told before the work starts and sends you a completion certificate afterwards. Keep both: solicitors ask for them when you sell.
A small alteration
A Minor Electrical Installation Works Certificate for a socket or light added to an existing circuit, again with the readings.
An inspection
An Electrical Installation Condition Report, with each observation coded C1, C2, C3 or FI. Landlords must give tenants a copy within 28 days.
If you did not get one
Ask. If the electrician cannot produce the test readings, the work was not tested. That is the point of the paper.