Add a basic test

src/args.rs

@@ -1,5 +1,8 @@
 use clap::{App, AppSettings, ArgMatches};
 
+#[cfg(test)]
+use clap::Result;
+
 
 fn build() -> App<'static, 'static> {
     return App::new(crate_name!())
@@ -17,3 +20,8 @@ fn build() -> App<'static, 'static> {
 pub fn get_matches() -> ArgMatches<'static> {
     return build().get_matches();
 }
+
+#[cfg(test)]
+pub fn get_matches_for(args : Vec<String>) -> Result<ArgMatches<'static>> {
+    return build().get_matches_from_safe(args);
+}

src/tests/args.rs

@@ -1,6 +1,7 @@
 use args;
 
 #[test]
-fn it_works() {
-    assert_eq!(4, 4);
+fn error_if_no_subcommand() {
+    let out = args::get_matches_for(vec!("mdp".into()));
+    assert!(out.is_err());
 }