Method test_seek0

Lib/test/test_codecs.py:2910–2963

(self)

class BomTest(unittest.TestCase):
    def test_seek0(self):
        data = "1234567890"
        tests = ("utf-16",
                 "utf-16-le",
                 "utf-16-be",
                 "utf-32",
                 "utf-32-le",
                 "utf-32-be")
        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
        for encoding in tests:
            # Check if the BOM is written only once
            with codecs_open_no_warn(os_helper.TESTFN, 'w+', encoding=encoding) as f:
                f.write(data)
                f.write(data)
                f.seek(0)
                self.assertEqual(f.read(), data * 2)
                f.seek(0)
                self.assertEqual(f.read(), data * 2)

            # Check that the BOM is written after a seek(0)
            with codecs_open_no_warn(os_helper.TESTFN, 'w+', encoding=encoding) as f:
                f.write(data[0])
                self.assertNotEqual(f.tell(), 0)
                f.seek(0)
                f.write(data)
                f.seek(0)
                self.assertEqual(f.read(), data)

            # (StreamWriter) Check that the BOM is written after a seek(0)
            with codecs_open_no_warn(os_helper.TESTFN, 'w+', encoding=encoding) as f:
                f.writer.write(data[0])
                self.assertNotEqual(f.writer.tell(), 0)
                f.writer.seek(0)
                f.writer.write(data)
                f.seek(0)
                self.assertEqual(f.read(), data)

            # Check that the BOM is not written after a seek() at a position
            # different than the start
            with codecs_open_no_warn(os_helper.TESTFN, 'w+', encoding=encoding) as f:
                f.write(data)
                f.seek(f.tell())
                f.write(data)
                f.seek(0)
                self.assertEqual(f.read(), data * 2)

            # (StreamWriter) Check that the BOM is not written after a seek()
            # at a position different than the start
            with codecs_open_no_warn(os_helper.TESTFN, 'w+', encoding=encoding) as f:
                f.writer.write(data)
                f.writer.seek(f.writer.tell())
                f.writer.write(data)
                f.seek(0)
                self.assertEqual(f.read(), data * 2)


bytes_transform_encodings = [