Test migration to jest by hand

Apparently using regular expressions is way easier.

test/getDaysDiffBetweenDates/getDaysDiffBetweenDates.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const getDaysDiffBetweenDates = require('./getDaysDiffBetweenDates.js');
+
+
+  test('getDaysDiffBetweenDates is a Function', () => {
+  expect(getDaysDiffBetweenDates).toBeInstanceOf(Function);
+});
+  t.equal(getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')), 9, "Returns the difference in days between two dates");
+