Index: tests/lean/test_single.sh
--- tests/lean/test_single.sh.orig
+++ tests/lean/test_single.sh
@@ -20,9 +20,9 @@ if [[ "$OSTYPE" == "msys" ]]; then
     ff=$(echo $ff  | sed 's|^/\([a-z]\)/|\1:/|' | sed 's|/|\\\\|g')
 fi
 
-DIFF=diff
+DIFF=gdiff
 if diff --color --help >/dev/null 2>&1; then
-  DIFF="diff --color";
+  DIFF="gdiff --color";
 fi
 
 echo "-- testing $f"