Strict output expectations

[gwenn]

Hello,
I am trying to use rexpect for testing rustyline.
But it seems that ANSI escape sequences are ignored in the output stream.
For example, I can remove this:

    p.exp_string("\x1b[?2004h")?; // bracketed paste on

with no impact on the tests.
But if I replace it with a typo:

    p.exp_string("\x1b[?2004x")?; // bracketed paste on

tests now fail.
Is there a way to tell rexpect to fail if an ANSI escape sequence is missing ?
Thanks.