diff --git a/kittens/choose_files/scan_test.go b/kittens/choose_files/scan_test.go
new file mode 100644
index 000000000..26c522121
--- /dev/null
+++ b/kittens/choose_files/scan_test.go
@@ -0,0 +1,25 @@
+package choose_files
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/kovidgoyal/kitty/tools/utils"
+)
+
+var _ = fmt.Print
+
+func TestAsLower(t *testing.T) {
+	buf := [512]byte{}
+	for _, q := range []string{
+		"abc", "aBc", "aBCCf83Dx", "mOoseÇa", "89ÇĞxxA", "", "23", "aIİBc",
+	} {
+		n := as_lower(q, buf[:])
+		actual := utils.UnsafeBytesToString(buf[:n])
+		if diff := cmp.Diff(strings.ToLower(q), actual); diff != "" {
+			t.Fatalf("Failed to lowercase: %#v\n%s", q, diff)
+		}
+	}
+}