Test migration to jest by hand

Apparently using regular expressions is way easier.

test/similarity/similarity.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const similarity = require('./similarity.js');
+
+
+  test('similarity is a Function', () => {
+  expect(similarity).toBeInstanceOf(Function);
+});
+  t.deepEqual(similarity([1, 2, 3], [1, 2, 4]), [1, 2], "Returns an array of elements that appear in both arrays.");
+