ran npm run tdd

test/once/once.js

@@ -1,8 +1,9 @@
-module.exports = once = fn => {
+const once = fn => {
 let called = false;
 return function(...args) {
 if (called) return;
 called = true;
 return fn.apply(this, args);
 };
-};
+};
+ module.exports = once