(Timeout): New exception.

(handler): New signal handler.
(TestCase): New class.
(TestCase.setUp): New setup function.  Reset the state of pcl_expect,
	and set up a SIGALRM timer.
(TestCase.tearDown): Cancel the SIGALRM timer.
(TestCase.progress): Re-arm the SIGALRM timer.
(TestCase.assertTimeDiff): New function.

test/base.py

+import signal
+import unittest
+
+import pcl_expect
+
+class Timeout(Exception): pass
+
+def handler(signo, stk):
+    raise Timeout()
+
+class TestCase(unittest.TestCase):
+    """Base class for most pcl-expect test suites.
+    """
+    def setUp(self):
+        """Reset state in pcl_expect, and arm the timeout."""
+        pcl_expect.reset_state()
+        signal.signal(signal.SIGALRM, handler)
+        self.progress()
+
+    def tearDown(self):
+        """Cancel the timeout."""
+        signal.alarm(0)
+
+    def progress(self):
+        """Re-arm the timeout.
+
+        Test cases that are expected to take a long time to run may
+        use this method -- but only if they are absolutely certain
+        that they cannot be running in an endless loop.
+        """
+
+        signal.alarm(20)
+
+    def assertTimeDiff(self, t0, t1, expected):
+        """Report an error unless two times differ the expected amount.
+
+        Compute t1-t0, and compare it to expected.  If they the
+        expected differance is more than 0.2 seconds off, raise an
+        error.
+        """
+
+        diff = t1-t0
+        err = abs(diff-expected)
+        if err > 0.2:
+            self.fail('wrong time difference %g, expected %g' % (
+                diff, expected))