Present desktop OTP and sensitive outputs

crates/storage/tests/presentation.rs

@@ -2,6 +2,7 @@
 
 use std::{
     error::Error,
+    io::Cursor,
     sync::{Arc, Mutex},
     time::Duration,
 };
@@ -229,3 +230,39 @@ fn qr_matrices_round_trip_and_render_without_plaintext() -> TestResult {
     ));
     Ok(())
 }
+
+#[test]
+fn qr_image_import_returns_secret_bytes_and_rejects_invalid_input() -> TestResult {
+    let payload = SecretBytes::new(
+        b"otpauth://totp/Example:alice?secret=JBSWY3DPEHPK3PXP&issuer=Example".to_vec(),
+    );
+    let matrix = QrMatrix::encode(&payload)?;
+    let scale = 8_u32;
+    let quiet = 4_u32;
+    let size = (matrix.width() as u32 + quiet * 2) * scale;
+    let mut image = image::GrayImage::from_pixel(size, size, image::Luma([255]));
+    for y in 0..matrix.width() {
+        for x in 0..matrix.width() {
+            if matrix.is_dark(x, y) == Some(true) {
+                for dy in 0..scale {
+                    for dx in 0..scale {
+                        image.put_pixel(
+                            (x as u32 + quiet) * scale + dx,
+                            (y as u32 + quiet) * scale + dy,
+                            image::Luma([0]),
+                        );
+                    }
+                }
+            }
+        }
+    }
+    let mut encoded = Cursor::new(Vec::new());
+    image.write_to(&mut encoded, image::ImageFormat::Png)?;
+    let decoded = QrMatrix::decode_image(&SecretBytes::new(encoded.into_inner()))?;
+    assert_eq!(decoded.expose(), payload.expose());
+    assert!(matches!(
+        QrMatrix::decode_image(&SecretBytes::new(b"not an image".to_vec())),
+        Err(QrError::InvalidImage)
+    ));
+    Ok(())
+}