test-lib: set $TRASH_DIRECTORY earlier

diff --git a/t/t4039-diff-assume-unchanged.sh b/t/t4039-diff-assume-unchanged.sh
index 23c0e357a765f00d807938fccf81a250c371ec4f..53ac44b0f0036803b48979c3c5f343ca02b1b80a 100755 (executable)
--- a/t/t4039-diff-assume-unchanged.sh
+++ b/t/t4039-diff-assume-unchanged.sh
@@ -34,9 +34,8 @@ test_expect_success POSIXPERM 'find-copies-harder is not confused by mode bits'
        git add exec &&
        git commit -m exec &&
        git update-index --assume-unchanged exec &&
-       >expect &&
        git diff-files --find-copies-harder -- exec >actual &&
-       test_cmp expect actual
+       test_must_be_empty actual
 '
 
 test_done