generate new test that did already exist & update all module snippets with declaration

test/powerset/powerset.js

@@ -1 +1 @@
-module.exports = arr => arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]);
+module.exports = powerset = arr => arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]);