def test_seek_read(self):
        with self.open(TESTFN, 'rb') as f:
            self.assertEqual(f.tell(), 0)
            self.assertEqual(f.read(1), b'z')
            self.assertEqual(f.tell(), 1)
            f.seek(0)
            self.assertEqual(f.tell(), 0)
            f.seek(0, 0)
            self.assertEqual(f.tell(), 0)
            f.seek(42)
            self.assertEqual(f.tell(), 42)
            f.seek(42, 0)
            self.assertEqual(f.tell(), 42)
            f.seek(42, 1)
            self.assertEqual(f.tell(), 84)
            f.seek(0, 1)
            self.assertEqual(f.tell(), 84)
            f.seek(0, 2)  # seek from the end
            self.assertEqual(f.tell(), size + 1 + 0)
            f.seek(-10, 2)
            self.assertEqual(f.tell(), size + 1 - 10)
            f.seek(-size-1, 2)
            self.assertEqual(f.tell(), 0)
            f.seek(size)
            self.assertEqual(f.tell(), size)
            # the 'a' that was written at the end of file above
            self.assertEqual(f.read(1), b'a')
            f.seek(-size-1, 1)
            self.assertEqual(f.read(1), b'z')
            self.assertEqual(f.tell(), 1)