Updated the test system

test/coalesceFactory.test.js

@@ -0,0 +1,10 @@
+const expect = require('expect');
+const {coalesceFactory} = require('./_30s.js');
+
+test('coalesceFactory is a Function', () => {
+  expect(coalesceFactory).toBeInstanceOf(Function);
+});
+const customCoalesce = coalesceFactory(_ => ![null, undefined, '', NaN].includes(_));
+test('Returns a customized coalesce function', () => {
+  expect(customCoalesce(undefined, null, NaN, '', 'Waldo')).toEqual('Waldo');
+});