Updated the test system

test/clampNumber.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const {clampNumber} = require('./_30s.js');
+
+test('clampNumber is a Function', () => {
+  expect(clampNumber).toBeInstanceOf(Function);
+});
+test('Clamps num within the inclusive range specified by the boundary values a and b', () => {
+  expect(clampNumber(2, 3, 5)).toBe(3);
+});