Test migration to jest by hand

Apparently using regular expressions is way easier.

test/unionWith/unionWith.test.js

@@ -0,0 +1,10 @@
+const expect = require('expect');
+const unionWith = require('./unionWith.js');
+
+
+  test('unionWith is a Function', () => {
+  expect(unionWith).toBeInstanceOf(Function);
+});
+  t.deepEqual(unionWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0, 3.9], (a, b) => Math.round(a) === Math.round(b)), [1, 1.2, 1.5, 3, 0, 3.9], 'Produces the appropriate results');
+  
+