test(internal): sequence /api/settings/info responses for 5xx restart probe

The test_5xx flow hits the info endpoint three times — loadTools init,
restartAddon's pre-POST baseline capture, and _probeAddonRestarted
after the POST. The old single-response fixture returned the SAME
instance_id every time, so the probe never saw the flip and looped
until timeout, leaving reloads=0.

Adds a `responses: [...]` shape to the harness fetch_map: each match
on a URL pattern advances a per-pattern counter; the last entry sticks
after exhaustion (matches "the addon came back online and stays
online"). Test now provides baseline → baseline → flipped so the
probe terminates with restarted=true and the reload fires.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: kingpanther13

tests/js/harness.mjs

@@ -63,15 +63,19 @@ function readStdin() {
 }
 
 function buildFetchStub(fetchMap, fetches) {
+  // Per-pattern call counter for sequenced `responses: [...]` entries.
+  const counters = new Map();
   return async function fetch(url, init) {
     const method = (init && init.method) || "GET";
     const body = init && init.body != null ? String(init.body) : null;
     fetches.push({ url: String(url), method, body });
 
     let entry = null;
+    let matchedPattern = null;
     for (const [pattern, value] of Object.entries(fetchMap)) {
       if (String(url).includes(pattern)) {
         entry = value;
+        matchedPattern = pattern;
         break;
       }
     }
@@ -80,6 +84,14 @@ function buildFetchStub(fetchMap, fetches) {
       // route get a loud, predictable failure mode.
       entry = { status: 404, body: "" };
     }
+    // Sequenced responses: each call advances the index, the last entry
+    // sticks after exhaustion (matches the "addon comes back online and
+    // stays online" shape these probe loops need).
+    if (Array.isArray(entry.responses)) {
+      const idx = counters.get(matchedPattern) ?? 0;
+      counters.set(matchedPattern, idx + 1);
+      entry = entry.responses[Math.min(idx, entry.responses.length - 1)];
+    }
     if (entry.throw) {
       throw new TypeError(entry.throw);
     }

tests/src/unit/test_settings_ui_js_behavior.py

@@ -192,18 +192,23 @@ def test_5xx_response_falls_through_to_reload_cycle(
         through to the poll-and-reload cycle, not surface the 5xx as a
         config error.
         """
-        # Pre-restart info → baseline; post-restart info → flipped.
-        # The harness's fetch_map matches by substring on first hit; we
-        # use a single entry and rely on the JS calling info() again
-        # after restart fires.
+        # The script hits /api/settings/info three times in this flow:
+        #   1. loadTools() at script init (for the is_addon / is_sidecar
+        #      branch in the restart-notice copy)
+        #   2. restartAddon() pre-POST, to capture the baseline instance_id
+        #   3. _probeAddonRestarted() after the POST, to detect the flip
+        # The first two return baseline; the third (and any further probe
+        # iterations — the last entry sticks) returns the flipped id so
+        # the probe exits with restarted=true.
         fetches = {
             **DEFAULT_FETCHES,
             "/api/settings/restart": {"status": 503, "body": ""},
-            # Replace the default info route so the probe sees a NEW
-            # instance_id and exits the polling loop with restarted=true.
             "/api/settings/info": {
-                "status": 200,
-                "json": {"instance_id": "new-id-after-restart"},
+                "responses": [
+                    {"status": 200, "json": {"instance_id": "baseline-id"}},
+                    {"status": 200, "json": {"instance_id": "baseline-id"}},
+                    {"status": 200, "json": {"instance_id": "flipped-id"}},
+                ],
             },
         }
         result = run_script(