Exam: How to replace every word with a dummy one on demand?

Question

Many times, I need to print an exam with a public printer to check its format and layout. However, it would be great to have a switch that replaces all the text with dummy text so that the exam confidentiality couldn't be breached.

For the sake of completeness, it would be perfect if the long text can be replaced by a long dummy text and vice versa for the short question text. In other words, the replacement needs to be done on word basis.

\documentclass{exam}

\begin{document}
\begin{questions}
    \question[7] 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text.
    \begin{parts}
        \part[5] some text to be replaced by a dummy text
        \begin{subparts}
            \subpart[3] to be replaced by a dummy text
            \begin{subsubparts}
                \subsubpart[1] some question to be replaced by a dummy text
            \end{subsubparts}
        \end{subparts}
     \begin{choices}
        \choice a short text to be replaced by a short one.
     \end{choices}
    \end{parts}
\end{questions}
\end{document}

Answer 1

A brute-force (and quite slow) solution can be adapted from here: How to do multiple string replacements?

Basically, I'm defining an obfuscate environment, so every alphabetical character is replaced by a lowercase X

\documentclass{exam}
\usepackage{xstring}
\usepackage{environ}
\def\obfuscatetext{0}
\newcommand{\xeverywhere}[2]{%
    \expandafter\StrSubstitute\expandafter{\BODY}{#1}{#2}[\BODY]%
}
\NewEnviron{obfuscate}{{%
\ifnum\obfuscatetext=1 
    \expandarg
    \StrSubstitute{\BODY}{a}{x}[\BODY]%
    \xeverywhere{b}{x}%
    \xeverywhere{c}{x}%
    \xeverywhere{d}{x}%
    \xeverywhere{e}{x}%
    \xeverywhere{f}{x}%
    \xeverywhere{g}{x}%
    \xeverywhere{h}{x}%
    \xeverywhere{i}{x}%
    \xeverywhere{j}{x}%
    \xeverywhere{k}{x}%
    \xeverywhere{l}{x}%
    \xeverywhere{m}{x}%
    \xeverywhere{n}{x}%
    \xeverywhere{o}{x}%
    \xeverywhere{p}{x}%
    \xeverywhere{q}{x}%
    \xeverywhere{r}{x}%
    \xeverywhere{s}{x}%
    \xeverywhere{t}{x}%
    \xeverywhere{u}{x}%
    \xeverywhere{v}{x}%
    \xeverywhere{w}{x}%
    \xeverywhere{y}{x}%
    \xeverywhere{z}{x}%
    \xeverywhere{A}{x}%
    \xeverywhere{B}{x}%
    \xeverywhere{C}{x}%
    \xeverywhere{D}{x}%
    \xeverywhere{E}{x}%
    \xeverywhere{F}{x}%
    \xeverywhere{G}{x}%
    \xeverywhere{H}{x}%
    \xeverywhere{I}{x}%
    \xeverywhere{J}{x}%
    \xeverywhere{K}{x}%
    \xeverywhere{L}{x}%
    \xeverywhere{M}{x}%
    \xeverywhere{N}{x}%
    \xeverywhere{O}{x}%
    \xeverywhere{P}{x}%
    \xeverywhere{Q}{x}%
    \xeverywhere{R}{x}%
    \xeverywhere{S}{x}%
    \xeverywhere{T}{x}%
    \xeverywhere{U}{x}%
    \xeverywhere{V}{x}%
    \xeverywhere{W}{x}%
    \xeverywhere{Y}{x}%
    \xeverywhere{X}{x}%
    \xeverywhere{Z}{x}%
    \BODY
\else 
    \BODY
\fi 
}}
\let\oldtextbf\textbf
\let\oldtextit\textit
\let\oldtexttt\texttt
\renewcommand{\textbf}[1]{\oldtextbf{\begin{obfuscate}#1\end{obfuscate}}}
\renewcommand{\textit}[1]{\oldtextit{\begin{obfuscate}#1\end{obfuscate}}}
\renewcommand{\texttt}[1]{\oldtexttt{\begin{obfuscate}#1\end{obfuscate}}}
\newcommand{\ObfuscateON}{%
\renewcommand{\obfuscatetext}{1}
}
\newcommand{\ObfuscateOFF}{%
    \renewcommand{\obfuscatetext}{0}
}
\ObfuscateON
\begin{document}
%If I want normal text, I just delete the next line:
\ObfuscateON
\begin{obfuscate}
\begin{questions}
    \question[7] 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text.
    \begin{parts}
        \part[5] some text to be replaced by a dummy text
        \begin{subparts}
            \subpart[3] to be replaced by a dummy text
            \begin{subsubparts}
                \subsubpart[1] some question to be replaced by a dummy text
            \end{subsubparts}
        \end{subparts}
     \begin{choices}
        \choice a short text to be replaced by a short one.
     \end{choices}
    \end{parts}
\end{questions}
\end{obfuscate}
\end{document}

Numbers and punctuation signs can be added ad libitum in the definition of obfuscate

EDIT: I added the \ObfuscateON command. obfuscate will do nothing by default, so it will only work if \ObfuscateON is used. I also patched the definitions of \textbf, \textit, and \texttt so obfuscate works.

EDIT AGAIN: As my first solution has so many bugs, I've come up with a nice solution using lualatex and chickenize which avoid clashes with other packages. As for graphics, using draft option suffices.

%!TEX program = lualatex
\documentclass{exam}
\usepackage{luacode}
\usepackage[draft]{graphicx}
\usepackage{chickenize}
\begin{luacode*}
    chickenizefraction = 100000
    chickenstring[1] = "ayyyy"
    chickenstring[2] = "lol"
    chickenstring[3] = "lmao"
    chickenstring[4] = "haha"
\end{luacode*}
\begin{document}
%Delete chickenize or use \unchickenize to get normal text
\chickenize
\begin{questions}
    \question[7] 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text. 
    some  very long question body to be replaced by a very long dummy text.
    \begin{parts}
        \part[5] some text to be replaced by a dummy text
        \begin{subparts}
            \subpart[3] to be replaced by a dummy text
            \begin{subsubparts}
                \subsubpart[1] some question to be replaced by a dummy text
            \end{subsubparts}
        \end{subparts}
     \begin{choices}
        \choice a short text to be replaced by a short one.
     \end{choices}
    \end{parts}
\end{questions}
\end{document}