"use strict"; const assert = require("node:assert/strict"); const {make_stub} = require("./lib/stub"); const {run_test, noop} = require("./lib/test"); /* The previous example was a bit extreme. Generally we just use the make_stub helper that comes with zjsunit. We will step away from the actual Zulip codebase for a second and just explore a contrived example. */ run_test("explore make_stub", ({override}) => { // Let's say you have to test the following code. const app = { /* istanbul ignore next */ notify_server_of_deposit(deposit_amount) { // simulate difficulty throw new Error(`We cannot report this value without wifi: ${deposit_amount}`); }, /* istanbul ignore next */ pop_up_fancy_confirmation_screen(deposit_amount, label) { // simulate difficulty throw new Error(`We cannot make a ${label} dialog for amount ${deposit_amount}`); }, }; let balance = 40; function deposit_paycheck(paycheck_amount) { balance += paycheck_amount; app.notify_server_of_deposit(paycheck_amount); app.pop_up_fancy_confirmation_screen(paycheck_amount, "paycheck"); } // Our deposit_paycheck should be easy to unit test for its // core functionality (updating your balance), but the side // effects get in the way. We have to override them to do // the simple test here. override(app, "notify_server_of_deposit", noop); override(app, "pop_up_fancy_confirmation_screen", noop); deposit_paycheck(10); assert.equal(balance, 50); // But we can do a little better here. Even though // the two side-effect functions are awkward here, we can // at least make sure they are invoked correctly. Let's // use stubs. const notify_stub = make_stub(); const pop_up_stub = make_stub(); // This time we'll just use our override helper to connect the // stubs. override(app, "notify_server_of_deposit", notify_stub.f); override(app, "pop_up_fancy_confirmation_screen", pop_up_stub.f); deposit_paycheck(25); assert.equal(balance, 75); assert.deepEqual(notify_stub.get_args("amount"), {amount: 25}); assert.deepEqual(pop_up_stub.get_args("amount", "label"), {amount: 25, label: "paycheck"}); });