You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: parse_input.rs
    path of file: ./repos/bnf/tests
    
    the code of the file until where you have to start completion: #![cfg(test)]

use bnf::Grammar;
use insta::assert_snapshot;

#[test]
fn undefined_prod() {
    let grammar: Grammar = "
        <start> ::= <a> | <b>
        <a> ::= 'a'
        "
    .parse()
    .unwrap();

    let input = "a";

    let parses: Vec<_> = grammar.parse_input(input).map(|a| a.to_string()).collect();
    assert_snapshot!(parses.join("\n"));
}

#[test]
fn dna_left_recursiv
    
fn mermaid_math_parse_tree() {
    let grammar: Grammar = "<sum> ::= <sum> <add> <product>
            <sum> ::= <product>
            <product> ::= <product> <mult> <factor>
            <product> ::= <factor>
            <add> ::= '+' | '-'
            <mult> ::= '*' | '/'
            <factor> ::= '(' <sum> ')'
            <factor> ::= <number>
            <number> ::= <digit> <number>
            <number> ::= <digit>
            <digit> ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
        "
    .parse()
    .unwrap();

    let input = "1+(2*3-4)";

    let mermaid: Vec<_> = grammar
        .parse_input(input)
        .map(|a| a.mermaid().to_string())
        .collect();
    assert_snapshot!(mermaid.join("\n"));
}