expect_decode_err
expect_decode_err(test, "Zg=!", 4, true, BASE64_STD);
expect_decode_err(test, "Zm$=", 4, true, BASE64_STD);
expect_decode_err(test, "Z===", 4, true, BASE64_STD);
expect_decode_err(test, "Zg", 2, true, BASE64_STD);
expect_decode_err(test, "Zm9v====", 8, true, BASE64_STD);
expect_decode_err(test, "Zm==A", 5, true, BASE64_STD);
expect_decode_err(test, with_nul, 4, true, BASE64_STD);
expect_decode_err(test, "Zg=!", 4, false, BASE64_STD);
expect_decode_err(test, "Zm$=", 4, false, BASE64_STD);
expect_decode_err(test, "Z===", 4, false, BASE64_STD);
expect_decode_err(test, "Zg=", 3, false, BASE64_STD);
expect_decode_err(test, "Zm9v====", 8, false, BASE64_STD);
expect_decode_err(test, "Zm==v", 4, false, BASE64_STD);
expect_decode_err(test, with_nul, 4, false, BASE64_STD);