test: deepen and complete project-wide test coverage (#297)

* test: deepen coverage for health doctor provider and tunnels

* test: add broad trait and module re-export coverage

src/tunnel/none.rs

@@ -26,3 +26,39 @@ impl Tunnel for NoneTunnel {
         None
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn name_is_none() {
+        let tunnel = NoneTunnel;
+        assert_eq!(tunnel.name(), "none");
+    }
+
+    #[tokio::test]
+    async fn start_returns_local_url() {
+        let tunnel = NoneTunnel;
+        let url = tunnel.start("127.0.0.1", 7788).await.unwrap();
+        assert_eq!(url, "http://127.0.0.1:7788");
+    }
+
+    #[tokio::test]
+    async fn stop_is_noop_success() {
+        let tunnel = NoneTunnel;
+        assert!(tunnel.stop().await.is_ok());
+    }
+
+    #[tokio::test]
+    async fn health_check_is_always_true() {
+        let tunnel = NoneTunnel;
+        assert!(tunnel.health_check().await);
+    }
+
+    #[test]
+    fn public_url_is_always_none() {
+        let tunnel = NoneTunnel;
+        assert!(tunnel.public_url().is_none());
+    }
+}