A properly made solder connection DOES NOT depend on the solder to make the
connection.
110.14(B) "... Soldered splices shall first be spliced or joined so as to be
mechanically and electrically secure without solder and then be soldered ..."
I know this may be a lost art in these days of wave soldering and low current
devices but back in the olden days electricians made the connection up tight
enough to make do on it's own, then they soldered it. There should be
significant copper to copper connection and if the solder was all gone the
connection should still be solid.