[wip] unit testing

- minor refactoring

src/file/chunk.rs

@@ -76,7 +76,10 @@ mod tests {
             );
             check_trait(format!("{chunk:?}"), repr_expect, "Debug", "Chunk");
 
-            assert_eq!(chunk.get_file_id().to_string(), "");
+            assert_eq!(
+                chunk.get_file_id().to_string(),
+                sharry::FileID::default().to_string()
+            );
             assert_eq!(chunk.get_offset(), mock_offset);
             assert_eq!(chunk.get_data(), data);
             assert_eq!(chunk.get_length(), len);

src/test_util/mock_ids.rs

@@ -122,20 +122,21 @@ mod tests {
         let share_id = ShareID::from(true);
         let file_id = FileID::from(true);
 
-        assert!(matches!((&uri, &alias_id).check(), Ok(())));
-        assert!(matches!(share_id.check(), Ok(())));
-        assert!(matches!((&share_id, &file_id).check(), Ok(())));
+        assert!((&uri, &alias_id).check().is_ok());
+        assert!(share_id.check().is_ok());
+        assert!((&share_id, &file_id).check().is_ok());
     }
 
     #[test]
     fn default_is_valid() {
         let uri = Uri::default();
+        let alias_id = AliasID::from(true); // no `impl Default`
         let share_id = ShareID::default();
         let file_id = FileID::default();
 
-        assert!(matches!((&uri, &AliasID::from(true)).check(), Ok(())));
-        assert!(matches!(share_id.check(), Ok(())));
-        assert!(matches!((&share_id, &file_id).check(), Ok(())));
+        assert!((&uri, &alias_id).check().is_ok());
+        assert!(share_id.check().is_ok());
+        assert!((&share_id, &file_id).check().is_ok());
     }
 
     #[test]