Test getsignal() and some error conditions

Lib/test/test_signal.py

 # Test the signal module
-from test.test_support import verbose, TestSkipped, TestFailed
+from test.test_support import verbose, TestSkipped, TestFailed, vereq
 import signal
 import os, sys, time
 
@@ -43,6 +43,28 @@ usr1 = signal.signal(signal.SIGUSR1, handlerB)
 usr2 = signal.signal(signal.SIGUSR2, signal.SIG_IGN)
 alrm = signal.signal(signal.SIGALRM, signal.default_int_handler)
 
+vereq(signal.getsignal(signal.SIGHUP), handlerA)
+vereq(signal.getsignal(signal.SIGUSR1), handlerB)
+vereq(signal.getsignal(signal.SIGUSR2), signal.SIG_IGN)
+
+try:
+    signal.signal(4242, handlerB)
+    raise TestFailed, 'expected ValueError for invalid signal # to signal()'
+except ValueError:
+    pass
+
+try:
+    signal.getsignal(4242)
+    raise TestFailed, 'expected ValueError for invalid signal # to getsignal()'
+except ValueError:
+    pass
+
+try:
+    signal.signal(signal.SIGUSR1, None)
+    raise TestFailed, 'expected TypeError for non-callable'
+except TypeError:
+    pass
+
 try:
     os.system(script)