fix(test): add magic number check on image tests

Signed-off-by: WoodenMaiden <[email protected]>

initramfs/src/image.rs

@@ -179,6 +179,8 @@ impl Image {
 #[cfg(test)]
 mod test {
     use std::env;
+    use std::io;
+    use std::io::Read;
     use std::{error::Error, result::Result};
 
     use super::Image;
@@ -211,12 +213,6 @@ mod test {
         assert_eq!(image2.tag(), "latest");
     }
 
-    #[test]
-    pub fn invalid_image_name() {
-        let image = Image::new("invalid_image_name");
-        assert!(image.is_err());
-    }
-
     #[test]
     pub fn test_initramfs_export() {
         // setup
@@ -249,11 +245,21 @@ mod test {
             )
             .is_ok());
 
+        let generated_file = File::open(&generated_filename);
+
         assert!(std::path::Path::new(&generated_filename).exists());
-        assert!(File::open(&generated_filename).is_ok());
+        assert!(generated_file.is_ok());
+
+        let magic_number = generated_file
+            .unwrap()
+            .bytes()
+            .take(2)
+            .map(|b| b.unwrap())
+            .collect::<Vec<u8>>();
 
         let kind = infer::get_from_path(&generated_filename).unwrap().unwrap();
         assert_eq!(kind.matcher_type(), infer::MatcherType::Archive);
+        assert_eq!(magic_number, &[0x1F, 0x8b]);
 
         // clean
         files.iter().for_each(|f| std::fs::remove_file(f).unwrap());