Add 3mf test

src/lib.rs

@@ -557,4 +557,29 @@ mod tests {
 
         assert_ne!(0, size);
     }
+
+    #[test]
+    fn cube_3mf() {
+        let img_filename = "cube-3mf.png".to_string();
+        let config = Config {
+            stl_filename: "test_data/cube.3mf".to_string(),
+            img_filename: img_filename.clone(),
+            format: image::ImageOutputFormat::Png,
+            ..Default::default()
+        };
+
+        match fs::remove_file(&img_filename) {
+            Ok(_) => (),
+            Err(ref error) if error.kind() == ErrorKind::NotFound => (),
+            Err(_) => {
+                panic!("Couldn't clean files before testing");
+            }
+        }
+
+        render_to_file(&config).expect("Error in render function");
+
+        let size = fs::metadata(img_filename).expect("No file created").len();
+
+        assert_ne!(0, size);
+    }
 }