test(qa): synchronize parser descendant timeout fixture

tools/summarizer/tests/test_app.py

@@ -5,6 +5,7 @@ import os
 import subprocess
 import sys
 import textwrap
+import time
 import zipfile
 from pathlib import Path
 
@@ -759,6 +760,7 @@ def test_parser_timeout_terminates_descendants(monkeypatch, tmp_path):
     child.write_text(textwrap.dedent(f"""
         import subprocess, sys, time
         from pathlib import Path
+        time.sleep(0.3)
         descendant = subprocess.Popen([sys.executable, '-c', 'import time; time.sleep(30)'])
         Path({str(pid_path)!r}).write_text(str(descendant.pid), encoding='ascii')
         time.sleep(30)
@@ -766,6 +768,23 @@ def test_parser_timeout_terminates_descendants(monkeypatch, tmp_path):
     monkeypatch.setattr(module, "PARSER_CHILD_PATH", child)
     monkeypatch.setattr(module, "PARSER_TIMEOUT_SECONDS", 0.2)
 
+    # Start the deadline only after this fixture has a descendant to terminate.
+    original_popen = subprocess.Popen
+
+    def ready_parser(*args, **kwargs):
+        process = original_popen(*args, **kwargs)
+        if len(args[0]) > 1 and args[0][1] == str(child):
+            deadline = time.monotonic() + 5
+            while not pid_path.exists() and process.poll() is None and time.monotonic() < deadline:
+                time.sleep(0.01)
+            if not pid_path.exists():
+                module._terminate_parser_process(process)
+                process.wait(timeout=5)
+                raise AssertionError("Parser fixture did not create its descendant")
+        return process
+
+    monkeypatch.setattr(module.subprocess, "Popen", ready_parser)
+
     try:
         module._run_parser_child(".txt", b"safe")
     except module.HTTPException as exc: