diff?

(diff? <file1> <file2>)

(diff? <file1> <file2>) is similar to (diff <file1> <file2>) except that <file2> should be produced by a part of the same action rather than be a dependency, is optional and will be consumed by diff?.

Example:

(progn
 (with-stdout-to test.output (run ./test.exe))
 (diff? test.expected test.output))