Updated the test system

test/intersectionWith.test.js

@@ -0,0 +1,15 @@
+const expect = require('expect');
+const {intersectionWith} = require('./_30s.js');
+
+test('intersectionWith is a Function', () => {
+  expect(intersectionWith).toBeInstanceOf(Function);
+});
+test('Returns a list of elements that exist in both arrays, using a provided comparator function', () => {
+  expect(
+    intersectionWith(
+      [1, 1.2, 1.5, 3, 0],
+      [1.9, 3, 0, 3.9],
+      (a, b) => Math.round(a) === Math.round(b)
+    )
+  ).toEqual([1.5, 3, 0]);
+});