fix: harden server start/stop guards

1 files changed, 17 insertions, 0 deletions

diff --git a/app/tests/test_backends_servers.py b/app/tests/test_backends_servers.py
index 8eaf53f..ab05eed 100644
--- a/app/tests/test_backends_servers.py
+++ b/app/tests/test_backends_servers.py
@@ -35,6 +35,23 @@ class StartTests(unittest.TestCase):
             self.assertTrue(servers.start(self.spec))
         mk.assert_not_called()
 
+    def test_refuses_to_double_start_while_previous_boot_is_alive(self):
+        """A live pid file blocks a second spawn of the same server.
+
+        A previous ``start`` whose server is still booting must not be
+        orphaned by a duplicate process on the same port.
+        """
+        pid_file = self.dir / "test-server.pid"
+        pid_file.write_text("4242", encoding="utf-8")
+        with patch.object(servers, "LOG_DIR", self.dir), \
+                patch.object(servers, "_pid_alive", return_value=True), \
+                patch("subprocess.Popen") as mk, \
+                patch("backends.common.server_running", return_value=False):
+            ok = servers.start(self.spec)
+        self.assertFalse(ok)
+        mk.assert_not_called()
+        self.assertTrue(pid_file.exists())
+
     def test_happy_path_spawns_and_polls_until_ready(self):
         proc = MagicMock()
         proc.pid = 4242