value can be changed string is truncated at nul character created with an empty string value can be changed string is truncated at nul character created with an empty string
import unittest
from ctypes import (create_string_buffer, create_unicode_buffer,
                    sizeof, byref, c_char, c_wchar)


class StringArrayTestCase(unittest.TestCase):
    def test(self):
        BUF = c_char * 4

        buf = BUF(b"a", b"b", b"c")
        self.assertEqual(buf.value, b"abc")
        self.assertEqual(buf.raw, b"abc\000")

        buf.value = b"ABCD"
        self.assertEqual(buf.value, b"ABCD")
        self.assertEqual(buf.raw, b"ABCD")

        buf.value = b"x"
        self.assertEqual(buf.value, b"x")
        self.assertEqual(buf.raw, b"x\000CD")

        buf[1] = b"Z"
        self.assertEqual(buf.value, b"xZCD")
        self.assertEqual(buf.raw, b"xZCD")

        self.assertRaises(ValueError, setattr, buf, "value", b"aaaaaaaa")
        self.assertRaises(TypeError, setattr, buf, "value", 42)

    def test_create_string_buffer_value(self):
        buf = create_string_buffer(32)

        buf.value = b"Hello, World"
        self.assertEqual(buf.value, b"Hello, World")

        self.assertRaises(TypeError, setattr, buf, "value", memoryview(b"Hello, World"))
        self.assertRaises(TypeError, setattr, buf, "value", memoryview(b"abc"))
        self.assertRaises(ValueError, setattr, buf, "raw", memoryview(b"x" * 100))

    def test_create_string_buffer_raw(self):
        buf = create_string_buffer(32)

        buf.raw = memoryview(b"Hello, World")
        self.assertEqual(buf.value, b"Hello, World")
        self.assertRaises(TypeError, setattr, buf, "value", memoryview(b"abc"))
        self.assertRaises(ValueError, setattr, buf, "raw", memoryview(b"x" * 100))

    def test_param_1(self):
        BUF = c_char * 4
        buf = BUF()

    def test_param_2(self):
        BUF = c_char * 4
        buf = BUF()

    def test_del_segfault(self):
        BUF = c_char * 4
        buf = BUF()
        with self.assertRaises(AttributeError):
            del buf.raw


class WStringArrayTestCase(unittest.TestCase):
    def test(self):
        BUF = c_wchar * 4

        buf = BUF("a", "b", "c")
        self.assertEqual(buf.value, "abc")

        buf.value = "ABCD"
        self.assertEqual(buf.value, "ABCD")

        buf.value = "x"
        self.assertEqual(buf.value, "x")

        buf[1] = "Z"
        self.assertEqual(buf.value, "xZCD")

    @unittest.skipIf(sizeof(c_wchar) < 4,
                     "sizeof(wchar_t) is smaller than 4 bytes")
    def test_nonbmp(self):
        u = chr(0x10ffff)
        w = c_wchar(u)
        self.assertEqual(w.value, u)


class WStringTestCase(unittest.TestCase):
    def test_wchar(self):
        c_wchar("x")
        repr(byref(c_wchar("x")))
        c_wchar("x")

    def test_basic_wstrings(self):
        cs = create_unicode_buffer("abcdef")
        self.assertEqual(cs.value, "abcdef")

        
        cs.value = "abc"
        self.assertEqual(cs.value, "abc")

        
        cs.value = "def\0z"
        self.assertEqual(cs.value, "def")

        self.assertEqual(create_unicode_buffer("abc\0def").value, "abc")

        
        cs = create_unicode_buffer(3)
        self.assertEqual(cs.value, "")

        cs.value = "abc"
        self.assertEqual(cs.value, "abc")

    def test_toolong(self):
        cs = create_unicode_buffer("abc")
        with self.assertRaises(ValueError):
            cs.value = "abcdef"

        cs = create_unicode_buffer(4)
        with self.assertRaises(ValueError):
            cs.value = "abcdef"


def run_test(rep, msg, func, arg):
    items = range(rep)
    from time import perf_counter as clock
    start = clock()
    for i in items:
        func(arg); func(arg); func(arg); func(arg); func(arg)
    stop = clock()
    print("%20s: %.2f us" % (msg, ((stop-start)*1e6/5/rep)))


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