test(snapshots): Add unit tests for pixel limit validation

Cover passing, boundary, single violation, multiple violations,
and empty input cases for validate_image_sizes.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: NicoHinderling

src/commands/build/snapshots.rs

@@ -314,3 +314,58 @@ fn upload_images(
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn make_image(name: &str, width: u32, height: u32) -> ImageInfo {
+        ImageInfo {
+            path: PathBuf::from(name),
+            relative_path: PathBuf::from(name),
+            width,
+            height,
+        }
+    }
+
+    #[test]
+    fn test_validate_image_sizes_passes_under_limit() {
+        let images = vec![
+            make_image("small.png", 1000, 1000),
+            make_image("medium.png", 5000, 7999),
+        ];
+        assert!(validate_image_sizes(&images).is_ok());
+    }
+
+    #[test]
+    fn test_validate_image_sizes_passes_at_limit() {
+        let images = vec![make_image("exact.png", 8000, 5000)];
+        assert!(validate_image_sizes(&images).is_ok());
+    }
+
+    #[test]
+    fn test_validate_image_sizes_fails_over_limit() {
+        let images = vec![
+            make_image("ok.png", 100, 100),
+            make_image("too_big.png", 8001, 5000),
+        ];
+        let err = validate_image_sizes(&images).unwrap_err();
+        assert!(err.to_string().contains("1 image exceeded"));
+    }
+
+    #[test]
+    fn test_validate_image_sizes_reports_multiple_violations() {
+        let images = vec![
+            make_image("big1.png", 10000, 5000),
+            make_image("big2.png", 8000, 6000),
+        ];
+        let err = validate_image_sizes(&images).unwrap_err();
+        assert!(err.to_string().contains("2 images exceeded"));
+    }
+
+    #[test]
+    fn test_validate_image_sizes_empty_list() {
+        let images: Vec<ImageInfo> = vec![];
+        assert!(validate_image_sizes(&images).is_ok());
+    }
+}