feat(seance): test failure cases for generate_hpgl

Author: Laura7089

seance/src/hpgl.rs

@@ -124,4 +124,20 @@ mod tests {
         assert_eq!(&pen_change(idx), expected);
         // TODO: what is the desired behaviour for usize::MAX ?
     }
+
+    #[test]
+    fn test_generate_hpgl_failures() {
+        let mut passes = crate::default_passes::default_passes();
+
+        assert_eq!(
+            generate_hpgl(&HashMap::new(), &passes),
+            "No tool passes enabled".to_string()
+        );
+
+        passes[0].set_enabled(true);
+        assert_eq!(
+            generate_hpgl(&HashMap::new(), &passes[0..5]),
+            "Exactly 16 tool passes are required".to_string()
+        )
+    }
 }