Add a test to reproduce a bug

Signed-off-by: ackintosh <sora.akatsuki@gmail.com>

src/encoding/protobuf.rs

@@ -567,6 +567,13 @@ mod tests {
             ])
             .inc();
 
+        family
+            .get_or_create(&vec![
+                ("method".to_string(), "POST".to_string()),
+                ("status".to_string(), "200".to_string()),
+            ])
+            .inc();
+
         let metric_set = encode(&registry).unwrap();
 
         let family = metric_set.metric_families.first().unwrap();
@@ -578,6 +585,7 @@ mod tests {
             extract_metric_type(&metric_set)
         );
 
+        // GET, 200
         let metric = family.metrics.first().unwrap();
         assert_eq!(2, metric.labels.len());
         assert_eq!("method", metric.labels[0].name);
@@ -594,6 +602,14 @@ mod tests {
             }
             _ => panic!("wrong value type"),
         }
+
+        // POST, 200
+        let metric = &family.metrics[1];
+        assert_eq!(2, metric.labels.len());
+        assert_eq!("method", metric.labels[0].name);
+        assert_eq!("POST", metric.labels[0].value);
+        assert_eq!("status", metric.labels[1].name);
+        assert_eq!("200", metric.labels[1].value);
     }
 
     #[test]