test_cmp "$TEST_DIRECTORY"/t4020/diff.NUL actual
'
+test_expect_success 'GIT_EXTERNAL_DIFF with more than one changed files' '
+ echo anotherfile > file2 &&
+ git add file2 &&
+ git commit -m "added 2nd file" &&
+ echo modified >file2 &&
+ GIT_EXTERNAL_DIFF=echo git diff
+'
+
test_done