I have not read the new law in Wales yet, come in December, but the English one says all the installation and non portable equipment needs testing except for the DNO head, however the IET guidance has always separated current using equipment (except lights) from the installation, so although both need testing, they are often not done at the same time, or even by the same person, the inspection and testing of in service electrical equipment often called PAT testing, training and exam was far less involved to the C&G 2391 taken before doing the EICR. In fact often done by semi-skilled guys.
The Emma Shaw case made it very clear semi-skilled should not do inspection and testing of the installation. But although case law seems to show one needs to be skilled, the English law says
“qualified person” means a person competent to undertake the inspection and testing required under regulation 3(1) and any further investigative or remedial work in accordance with the electrical safety standards;
nothing about how much experience or what qualifications need to be held.
Following that definition in spite having my C&G 2391 and trained to level 5 (degree standard) because of my injury, I can't guarantee to be able to do the remedial work, so suppose I should not do the testing and inspecting?
But
@flameport is spot on, in industrial premises where the EICR is done regular, doing a sample is the normal way, but as to how much is inspected is up to the client, for example the LABC may ask an inspector to look at an extension, and also instruct any breach of current regulations is high lighted, but the IET changed the coding removing code 4 which was does not comply with current regulations as being unhelpful.
The code C1 says it is dangerous, which is reasonable straight forward, but code C2 says potentially dangerous and all 230 volt is potentially dangerous, and C3 is improvement recommended. And it is up to the inspector to decide if any item not complying with current regulations is C2, C3 or not worth reporting. It is a professional opinion, there is no hard and fast rule.
Same goes for code FI or LIM, in real terms they mean the same, but FI is a fail, and LIM is not, but mean some thing not tested, call it further investigation required, or the investigation did not cover that item, really it means the same.
So there is nothing to stop me telling the guy inspecting my house, only do the socket circuits. It would not satisfy the new English law, but unless I tell the inspector I want it doing to satisfy the landlord law, then he is doing nothing wrong, it is not like an MOT where the government sets the standard, it is a wishy washy inspection which has no real rules as to how much or how little is inspected.
The has been court cases, trading standards Pembrokeshire took one guy to court, but remember that is in Wales, so not to do with the English law. Also the guy admitted he did not do a thorough inspection, but the result has been inspectors are considering if there by grace of god go I, so more attention is being taken.
@flameport comments are very true, this house I found a borrowed neutral on the lighting circuit likely existing from when the house was built, and only found when individual RCD's added to all circuits (RCBO) which tripped due to the error.
My daughter rented a house, and there was a problem, and I fixed it, but it was on the QT, so no paperwork raised, this is why IET says EICR should be done on change of occupant, one has no idea what some tenant before one has done, this is very different with industrial premises, I know a minor works certificate needs raising for any work done.
When doing my exam, I had a board to test, so no walking, just a sample of items found in a house, had I seem to remember an hour, and I felt not enough time, so yes can see at that standard it would take a couple of days, however in the main if some thing fails, you stop, if work needs doing, it will need retesting after, so if taken that long, likely most items have passed.