Function check_read_at_contract 

pub fn check_read_at_contract(
    source: &mut dyn DynReadAt,
    expected: &[u8],
) -> Conformance

Verify a DynReadAt driver source against the bytes it claims to serve: length, exact reads at the edges and middle, one batched out-of-order multi-range read, and an error (never a short or zero-filled read) past the end.