[fine] Many test improvements, error improvements

- Check for more error conditions
- Move to more definitive error assertions
- Simpler error messages in some cases
- Test more conditions more thoroughly, revisit old tests

fine/build.rs

@@ -37,8 +37,13 @@ fn generate_test_for_file(path: PathBuf) -> String {
         };
 
         let line = line.trim();
-        if line == "@ignore" {
-            disabled = quote! { #[ignore] };
+        if let Some(line) = line.strip_prefix("@ignore") {
+            let reason = line.trim();
+            assert_ne!(
+                reason, "",
+                "You need to provide at least some description for ignoring in {display_path}"
+            );
+            disabled = quote! { #[ignore = #reason] };
         } else if line == "@concrete:" {
             let mut concrete = String::new();
             while let Some(line) = lines.next() {