Updated the test system

test/truncateString.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const {truncateString} = require('./_30s.js');
+
+test('truncateString is a Function', () => {
+  expect(truncateString).toBeInstanceOf(Function);
+});
+test('Truncates a "boomerang" up to a specified length.', () => {
+  expect(truncateString('boomerang', 7)).toBe('boom...');
+});