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/health/mod.rs

@@ -104,3 +104,84 @@ pub fn snapshot_json() -> serde_json::Value {
         })
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn unique_component(prefix: &str) -> String {
+        format!("{prefix}-{}", uuid::Uuid::new_v4())
+    }
+
+    #[test]
+    fn mark_component_ok_initializes_component_state() {
+        let component = unique_component("health-ok");
+
+        mark_component_ok(&component);
+
+        let snapshot = snapshot();
+        let entry = snapshot
+            .components
+            .get(&component)
+            .expect("component should be present after mark_component_ok");
+
+        assert_eq!(entry.status, "ok");
+        assert!(entry.last_ok.is_some());
+        assert!(entry.last_error.is_none());
+    }
+
+    #[test]
+    fn mark_component_error_then_ok_clears_last_error() {
+        let component = unique_component("health-error");
+
+        mark_component_error(&component, "first failure");
+        let error_snapshot = snapshot();
+        let errored = error_snapshot
+            .components
+            .get(&component)
+            .expect("component should exist after mark_component_error");
+        assert_eq!(errored.status, "error");
+        assert_eq!(errored.last_error.as_deref(), Some("first failure"));
+
+        mark_component_ok(&component);
+        let recovered_snapshot = snapshot();
+        let recovered = recovered_snapshot
+            .components
+            .get(&component)
+            .expect("component should exist after recovery");
+        assert_eq!(recovered.status, "ok");
+        assert!(recovered.last_error.is_none());
+        assert!(recovered.last_ok.is_some());
+    }
+
+    #[test]
+    fn bump_component_restart_increments_counter() {
+        let component = unique_component("health-restart");
+
+        bump_component_restart(&component);
+        bump_component_restart(&component);
+
+        let snapshot = snapshot();
+        let entry = snapshot
+            .components
+            .get(&component)
+            .expect("component should exist after restart bump");
+
+        assert_eq!(entry.restart_count, 2);
+    }
+
+    #[test]
+    fn snapshot_json_contains_registered_component_fields() {
+        let component = unique_component("health-json");
+
+        mark_component_ok(&component);
+
+        let json = snapshot_json();
+        let component_json = &json["components"][&component];
+
+        assert_eq!(component_json["status"], "ok");
+        assert!(component_json["updated_at"].as_str().is_some());
+        assert!(component_json["last_ok"].as_str().is_some());
+        assert!(json["uptime_seconds"].as_u64().is_some());
+    }
+}