From 90eaa0bcc56392615e2f67076f0f1e01ce93a5d3 Mon Sep 17 00:00:00 2001
From: Marc Riegel <marc.riegel@nimbusforge.de>
Date: Tue, 7 Apr 2026 14:27:55 +0200
Subject: [PATCH] test: add add-before-start regression coverage

Closes #28
---
 CHANGELOG.md         |  2 ++
 tests/integration.rs | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b13be9..06faa57 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,8 @@ and its version numbers follow [Semantic Versioning](https://semver.org/).
   scheme (`<type>/<issue-id>-<short-kebab-description>`).
 - `AGENTS.md` PR title convention (no coding-agent/tool tags) and mandatory
   `git pull --ff-only origin main` before branch creation (`#32`).
+- Regression test coverage for runtime coordination contracts now explicitly
+  includes the `add()` pre-start panic behavior (`#28`).
 
 ### Changed
 - `process_handle()` now returns `Arc<dyn ProcessControlHandler>` (cheap cloning,
diff --git a/tests/integration.rs b/tests/integration.rs
index 15d7e14..ebc422c 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -300,6 +300,30 @@ async fn test_runnable() {
     );
 }
 
+#[test]
+fn test_add_before_start_panics_with_contract_message() {
+    let manager = ProcessManager::new();
+    let attempts = Arc::new(AtomicUsize::new(0));
+
+    let panic = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
+        manager.add(FlakyController::new(0, Arc::clone(&attempts)));
+    }))
+    .expect_err("add() before startup must panic");
+
+    let message = if let Some(s) = panic.downcast_ref::<&str>() {
+        (*s).to_owned()
+    } else if let Some(s) = panic.downcast_ref::<String>() {
+        s.clone()
+    } else {
+        "<non-string panic payload>".to_owned()
+    };
+
+    assert!(
+        message.contains("cannot call add() before manager has started"),
+        "unexpected panic message: {message}"
+    );
+}
+
 #[tokio::test]
 async fn test_shutdown_waits_for_child_termination() {
     let mut manager = ProcessManager::new();