Add test cases.

org_mode_samples/latex_fragment/fragment_vs_environment.org

@@ -0,0 +1,7 @@
+\begin{itemize}
+\item foo \sqrt{x}
+\end{itemize}
+
+\begin{itemize}
+\item bar \sqrt{y}
+\end{itemize} % Need text on this line to prevent it from becoming a LaTeX environment org-mode element

org_mode_samples/latex_fragment/math_mode.org

@@ -0,0 +1 @@
+tex can have math between dollar signs like $x^2=y$ and $$ x=+\sqrt{y} $$ but also braces and brackets like \( x=2 \) and \[ x=-\sqrt{2} \]

org_mode_samples/latex_fragment/simple.org

@@ -0,0 +1,4 @@
+\begin{itemize}
+% this would be a LaTeX comment if this was a LaTeX document
+\item Heres some math \sqrt{y}
+\end{itemize} % Need text on this line to prevent it from becoming a LaTeX environment org-mode element

src/parser/latex_fragment.rs

@@ -12,6 +12,7 @@ use crate::error::Res;
 use crate::parser::object::Entity;
 use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::util::get_consumed;
+use crate::parser::util::not_yet_implemented;
 use crate::parser::LatexFragment;
 
 #[tracing::instrument(ret, level = "debug")]
@@ -19,6 +20,7 @@ pub fn latex_fragment<'r, 's>(
     context: Context<'r, 's>,
     input: &'s str,
 ) -> Res<&'s str, LatexFragment<'s>> {
+    not_yet_implemented()?;
     let (remaining, _) = tag("\\")(input)?;
     todo!()
     // let (remaining, entity_name) = name(context, remaining)?;