Use sets to compare package.json files content

Order doesn't matter!

tests/manifest/main.rs

@@ -6,6 +6,7 @@ extern crate wasm_pack;
 
 mod utils;
 
+use std::collections::HashSet;
 use std::fs;
 
 use wasm_pack::manifest;
@@ -59,10 +60,17 @@ fn it_creates_a_package_json_default_path() {
         pkg.repository.url,
         "https://github.com/ashleygwilliams/wasm-pack.git"
     );
-    assert_eq!(pkg.files, ["wasm_pack_bg.wasm", "wasm_pack_bg.js", "wasm_pack.d.ts"]);
     assert_eq!(pkg.main, "wasm_pack.js");
     let types = pkg.types.unwrap_or_default();
     assert_eq!(types, "wasm_pack.d.ts");
+
+    let actual_files: HashSet<String> = pkg.files.into_iter().collect();
+    let expected_files: HashSet<String> = ["wasm_pack_bg.wasm", "wasm_pack_bg.js", "wasm_pack.d.ts"]
+        .iter()
+        .map(|&s| String::from(s))
+        .collect();
+    assert_eq!(actual_files, expected_files);
+
 }
 
 #[test]