Test dependency binary no longer found under unqualified name

Hi, so I have some code in https://github.com/sourcefrog/conserve/blob/master/tests/blackbox.rs#L215 that tries to run, from a test, a binary built by the enclosing crate. It simply looks for the conserve binary in the same directory as the blackbox test binary.

That has been working fine, but recently started failing on nightly, the difference apparently being that cargo test runs the test from inside target/debug/deps not target/debug, and in that context only the hash-qualified version of the conserve binary is present.

Strangely there is also a blackbox-6b1592d10fffb366 binary in target/debug (even after a clean build) and if I run that it does find the conserve from that directory.

Quite possibly I'm doing the wrong thing - any advice?

Another way to put this is: what's the difference between target/debug and target/debug/deps?

I would have guessed the latter is for indirect dependencies but then why does the black box test binary get run from there?