import os, io, fcntl, unittest

class TestBlockingIOError(unittest.TestCase):

    def _make_files(self):
        r, w = os.pipe()
        fcntl.fcntl(r, fcntl.F_SETFL, os.O_NDELAY)
        fcntl.fcntl(w, fcntl.F_SETFL, os.O_NDELAY)
        rf = io.open(r, mode='rb', closefd=True)
        wf = io.open(w, mode='wb', closefd=True)
        return rf, wf

    def test_read(self):
        rf, wf = self._make_files()
        with self.assertRaises(io.BlockingIOError):
            rf.read(1)
        
    def test_write(self):
        rf, wf = self._make_files()
        msg = b'X'*10000
        with self.assertRaises(io.BlockingIOError):
            while 1:
                wf.write(msg)

if __name__ == '__main__':
    unittest.main()