extern crate syn;

use std::env;
use std::fs::File;
use std::io::{Write, BufWriter};
use syn::DeriveInput;

pub fn generate_elm(_: &DeriveInput) {
    let mut path = env::current_dir().unwrap();
    path.push("generated/test.txt");

    let file = File::create(path).unwrap();
    let ref mut w = BufWriter::new(file);
    w.write("Hello, World!".as_bytes()).unwrap();
}

extern crate syn;

use syn::DeriveInput;

pub fn generate_elm(_: &DeriveInput) {
    // do nothing
}

--- 
+++ 
@@ -1,7 +1,15 @@
 extern crate syn;
 
+use std::env;
+use std::fs::File;
+use std::io::{Write, BufWriter};
 use syn::DeriveInput;
 
 pub fn generate_elm(_: &DeriveInput) {
-    // do nothing
+    let mut path = env::current_dir().unwrap();
+    path.push("generated/test.txt");
+
+    let file = File::create(path).unwrap();
+    let ref mut w = BufWriter::new(file);
+    w.write("Hello, World!".as_bytes()).unwrap();
 }
Write a test file to generated directory
