const sinon = require('sinon'); // package library used alongside @ciscospark.test-helper-chai const { assert } = require('@ciscospark/test-helper-chai'); // sample function to test function addNumbers(a, b) { return a + b } describe('addNumbers function', () => { let spy; beforeEach(() => { // create a spy for the addNumbers function spy = sinon.spy(addNumbers); }); it('should not call the function when the inputs are null', () => { // call the function addNumbers(null, null); // assert that the function was not called assert.notCalled(spy); }); it('should call the function when the inputs are numbers', () => { // call the function addNumbers(5, 10); // assert that the function was called once assert.calledOnce(spy); }); });In this example, the assert notCalled function is used to check that the `addNumbers` function is not called when the inputs are null. We create a spy on the `addNumbers` function using the Sinon library, and then call the function with null values. Finally, we use `assert.notCalled` to check that the function spy has not been called. The package library that works alongside @ciscospark.test-helper-chai in this example is sinon.