diff --git a/tests/io_op_test.py b/tests/io_op_test.py
new file mode 100644
index 00000000..8ec204b6
--- /dev/null
+++ b/tests/io_op_test.py
@@ -0,0 +1,119 @@
+
+import errno
+import select
+
+import mock
+import unittest2
+
+import testlib
+import mitogen.core
+
+
+class RestartTest(object):
+    func = staticmethod(mitogen.core.io_op)
+    exception_class = None
+
+    def test_eintr_restarts(self):
+        m = mock.Mock()
+        m.side_effect = [
+            self.exception_class(errno.EINTR),
+            self.exception_class(errno.EINTR),
+            self.exception_class(errno.EINTR),
+            'yay',
+        ]
+        rc, disconnected = self.func(m, 'input')
+        self.assertEquals(rc, 'yay')
+        self.assertFalse(disconnected)
+        self.assertEquals(4, m.call_count)
+        self.assertEquals(m.mock_calls, [
+            mock.call('input'),
+            mock.call('input'),
+            mock.call('input'),
+            mock.call('input'),
+        ])
+
+
+class SelectRestartTest(RestartTest, testlib.TestCase):
+    exception_class = select.error
+
+
+class OsErrorRestartTest(RestartTest, testlib.TestCase):
+    exception_class = OSError
+
+
+class DisconnectTest(object):
+    func = staticmethod(mitogen.core.io_op)
+    errno = None
+    exception_class = None
+
+    def test_disconnection(self):
+        m = mock.Mock()
+        m.side_effect = self.exception_class(self.errno)
+        rc, disconnected = self.func(m, 'input')
+        self.assertEquals(rc, None)
+        self.assertTrue(disconnected)
+        self.assertEquals(1, m.call_count)
+        self.assertEquals(m.mock_calls, [
+            mock.call('input'),
+        ])
+
+
+class SelectDisconnectEioTest(DisconnectTest, testlib.TestCase):
+    errno = errno.EIO
+    exception_class = select.error
+
+
+class SelectDisconnectEconnresetTest(DisconnectTest, testlib.TestCase):
+    errno = errno.ECONNRESET
+    exception_class = select.error
+
+
+class SelectDisconnectEpipeTest(DisconnectTest, testlib.TestCase):
+    errno = errno.EPIPE
+    exception_class = select.error
+
+
+class OsErrorDisconnectEioTest(DisconnectTest, testlib.TestCase):
+    errno = errno.EIO
+    exception_class = OSError
+
+
+class OsErrorDisconnectEconnresetTest(DisconnectTest, testlib.TestCase):
+    errno = errno.ECONNRESET
+    exception_class = OSError
+
+
+class OsErrorDisconnectEpipeTest(DisconnectTest, testlib.TestCase):
+    errno = errno.EPIPE
+    exception_class = OSError
+
+
+class ExceptionTest(object):
+    func = staticmethod(mitogen.core.io_op)
+    errno = None
+    exception_class = None
+
+    def test_exception(self):
+        m = mock.Mock()
+        m.side_effect = self.exception_class(self.errno)
+        e = self.assertRaises(self.exception_class,
+                              lambda: self.func(m, 'input'))
+        self.assertEquals(e, m.side_effect)
+        self.assertEquals(1, m.call_count)
+        self.assertEquals(m.mock_calls, [
+            mock.call('input'),
+        ])
+
+
+class SelectExceptionTest(ExceptionTest, testlib.TestCase):
+    errno = errno.EBADF
+    exception_class = select.error
+
+
+class OsErrorExceptionTest(ExceptionTest, testlib.TestCase):
+    errno = errno.EBADF
+    exception_class = OSError
+
+
+if __name__ == '__main__':
+    unittest2.main()