Handle case where Deferred fires after timeout

2 files changed, 39 insertions, 1 deletions

diff --git a/testtools/_spinner.py b/testtools/_spinner.py
index 425d478..fa1b18b 100644
--- a/testtools/_spinner.py
+++ b/testtools/_spinner.py
@@ -153,6 +153,7 @@ class Spinner(object):
         self._saved_signals = []
         self._junk = []
         self._debug = debug
+        self._spinning = False
 
     def _cancel_timeout(self):
         if self._timeout_call:
@@ -186,7 +187,10 @@ class Spinner(object):
 
     def _stop_reactor(self, ignored=None):
         """Stop the reactor!"""
-        self._reactor.crash()
+        # XXX: Would like to emit a warning when called when *not* spinning.
+        if self._spinning:
+            self._reactor.crash()
+            self._spinning = False
 
     def _timed_out(self, function, timeout):
         e = TimeoutError(function, timeout)
@@ -287,6 +291,7 @@ class Spinner(object):
                 d.addBoth(self._stop_reactor)
             try:
                 self._reactor.callWhenRunning(run_function)
+                self._spinning = True
                 self._reactor.run()
             finally:
                 self._reactor.stop = real_stop
diff --git a/testtools/tests/test_spinner.py b/testtools/tests/test_spinner.py
index 6e5d007..ef26c68 100644
--- a/testtools/tests/test_spinner.py
+++ b/testtools/tests/test_spinner.py
@@ -297,6 +297,39 @@ class TestRunInReactor(NeedsTwistedTestCase):
     def test_fast_sigint_raises_no_result_error_second_time(self):
         self.test_fast_sigint_raises_no_result_error()
 
+    def test_fires_after_timeout(self):
+        # If we timeout, but the Deferred actually ends up firing after the
+        # time out (perhaps because Spinner's clean-up code is buggy, or
+        # perhaps because the code responsible for the callback is in a
+        # thread), then the next run of a spinner works as intended,
+        # completely isolated from the previous run.
+
+        # Ensure we've timed out, and that we have a handle on the Deferred
+        # that didn't fire.
+        reactor = self.make_reactor()
+        spinner1 = self.make_spinner(reactor)
+        timeout = self.make_timeout()
+        deferred1 = defer.Deferred()
+        self.expectThat(
+            lambda: spinner1.run(timeout, lambda: deferred1),
+            Raises(MatchesException(_spinner.TimeoutError)))
+
+        # Make a Deferred that will fire *after* deferred1 as long as the
+        # reactor keeps spinning. We don't care that it's a callback of
+        # deferred1 per se, only that it strictly fires afterwards.
+        marker = object()
+        deferred2 = defer.Deferred()
+        deferred1.addCallback(
+            lambda ignored: reactor.callLater(0, deferred2.callback, marker))
+
+        def fire_other():
+            """Fire Deferred from the last spin while waiting for this one."""
+            deferred1.callback(object())
+            return deferred2
+
+        spinner2 = self.make_spinner(reactor)
+        self.assertThat(spinner2.run(3 * timeout, fire_other), Is(marker))
+
 
 def test_suite():
     from unittest import TestLoader