Test migration to jest by hand

Apparently using regular expressions is way easier.

test/powerset/powerset.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const powerset = require('./powerset.js');
+
+
+  test('powerset is a Function', () => {
+  expect(powerset).toBeInstanceOf(Function);
+});
+  t.deepEqual(powerset([1, 2]), [[], [1], [2], [2,1]], "Returns the powerset of a given array of numbers.");
+