Updated the test system

test/arrayToCSV.test.js

@@ -0,0 +1,12 @@
+const expect = require('expect');
+const {arrayToCSV} = require('./_30s.js');
+
+test('arrayToCSV is a Function', () => {
+  expect(arrayToCSV).toBeInstanceOf(Function);
+});
+test('arrayToCSV works with default delimiter', () => {
+  expect(arrayToCSV([['a', 'b'], ['c', 'd']])).toBe('"a","b"\n"c","d"');
+});
+test('arrayToCSV works with custom delimiter', () => {
+  expect(arrayToCSV([['a', 'b'], ['c', 'd']], ';')).toBe('"a";"b"\n"c";"d"');
+});