diff --git a/test/mechanicaldiff.bats b/test/mechanicaldiff.bats
index 7be9d9e..a76be55 100755
--- a/test/mechanicaldiff.bats
+++ b/test/mechanicaldiff.bats
@@ -93,3 +93,30 @@ setup() {
   assert_output --partial "+beta_changed"
   refute_output --partial "delta_changed"
 }
+
+@test "handles multiple files" {
+  printf "%s\n" "foo" >"$BATS_TEST_TMPDIR/old1"
+  printf "%s\n" "bar" >"$BATS_TEST_TMPDIR/new1"
+  printf "%s\n" "alpha" >"$BATS_TEST_TMPDIR/old2"
+  printf "%s\n" "beta" >"$BATS_TEST_TMPDIR/new2"
+
+  git diff --no-index "$BATS_TEST_TMPDIR/old1" "$BATS_TEST_TMPDIR/new1" \
+    >"$BATS_TEST_TMPDIR/diff_one" || true
+  git diff --no-index "$BATS_TEST_TMPDIR/old2" "$BATS_TEST_TMPDIR/new2" \
+    >"$BATS_TEST_TMPDIR/diff_two" || true
+
+  cat "$BATS_TEST_TMPDIR/diff_one" "$BATS_TEST_TMPDIR/diff_two" \
+    >"$BATS_TEST_TMPDIR/diff_all"
+
+  run mechanicaldiff.py foo bar <"$BATS_TEST_TMPDIR/diff_one"
+  assert_success
+  output_one="$output"
+
+  run mechanicaldiff.py foo bar <"$BATS_TEST_TMPDIR/diff_two"
+  assert_failure
+  output_two="$output"
+
+  run mechanicaldiff.py foo bar <"$BATS_TEST_TMPDIR/diff_all"
+  assert_failure
+  assert_output "${output_one}${output_two}"
+}