Test migration to jest by hand

Apparently using regular expressions is way easier.

test/unionBy/unionBy.js

@@ -0,0 +1,5 @@
+const unionBy = (a, b, fn) => {
+const s = new Set(a.map(v => fn(v)));
+return Array.from(new Set([...a, ...b.filter(x => !s.has(fn(x)))]));
+};
+module.exports = unionBy;

test/unionBy/unionBy.test.js

@@ -0,0 +1,10 @@
+const expect = require('expect');
+const unionBy = require('./unionBy.js');
+
+
+  test('unionBy is a Function', () => {
+  expect(unionBy).toBeInstanceOf(Function);
+});
+  t.deepEqual(unionBy([2.1], [1.2, 2.3], Math.floor), [2.1, 1.2], 'Produces the appropriate results');
+  
+