All of my Clojure projects use both Leiningen and expectations; therefore, my directory structures always look similar to what you see below.
source - /Users/jfields/src/project-name/src/clojure/
tests - /Users/jfields/src/project-name/test/clojure/expectations/
Since my projects follow this convention, I'm able to make several assumptions about where the expectations and where the source will actually live. If you don't use expectations, or you follow a slightly different directory structure, you'll want to hack this a bit to follow your conventions.
If you're in a source file, find (and open) the expectations.
If you're in a test file, find (and open) the source.