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: prefixer.rs
    path of file: ./repos/swc/crates/swc_css_prefixer/tests
    
    the code of the file until where you have to start completion: //! Tests ported from https://github.com/thysultan/stylis.js
//!
//! License is MIT, which is original license at the time of copying.
//! Original test authors have copyright for their work.
#![deny(warnings)]
#![allow(clippy::needless_update)]

use std::path::PathBuf;

use preset_env_base::query::{Query, Targets};
use swc_css_ast::Stylesheet;
use swc_css_codegen::{
    writer::basic::{BasicCssWriter, BasicCssWriterConfig},
    CodegenConfig, Emit,
};
use swc_css_parser::{parse_file, parser::ParserConfig};
use swc_css_prefixer::{options::Options, prefixer};
use swc_css_visit::VisitMutWith;
use testing::NormalizedOutput;

fn prefix(input: PathBuf, options: Options, suffix: Option<&str>) {
    let parent = input.parent().unwrap();
    let output = match suffix {
        Some(suffix) => parent.join("output.".to_owned() + suffix + ".
    
fn prefix(input: PathBuf, options: Options, suffix: Option<&str>) {
    let parent = input.parent().unwrap();
    let output = match suffix {
        Some(suffix) => parent.join("output.".to_owned() + suffix + ".css"),
        _ => parent.join("output.css"),
    };

    testing::run_test2(false, |cm, handler| {
        //
        let fm = cm.load_file(&input).unwrap();
        let mut errors = vec![];
        let mut ss: Stylesheet = parse_file(
            &fm,
            None,
            ParserConfig {
                allow_wrong_line_comments: true,
                ..Default::default()
            },
            &mut errors,
        )
        .unwrap();
        for err in errors {
            err.to_diagnostics(&handler).emit();
        }

        ss.visit_mut_with(&mut prefixer(options));

        let mut s = String::new();
        {
            let mut wr = BasicCssWriter::new(&mut s, None, BasicCssWriterConfig::default());
            let mut gen =
                swc_css_codegen::CodeGenerator::new(&mut wr, CodegenConfig { minify: false });

            gen.emit(&ss).unwrap();
        }

        NormalizedOutput::from(s).compare_to_file(&output).unwrap();

        Ok(())
    })
    .unwrap();
}