update manual assertions comments for chapter 3

Author: lucasfcosta

chapter3/2_writing_good_assertions/4_manual_assertions/inventoryController.js

@@ -14,6 +14,8 @@ const getInventory = () => {
     return { ...contents, [name]: quantity };
   }, {});
 
+  // To make the tests in this folder pass, update this
+  // line so that it doesn't set the new Date's year to 3000.
   return { ...contents, generatedAt: new Date(new Date().setYear(3000)) };
 };
 

chapter3/2_writing_good_assertions/4_manual_assertions/inventoryController.test.js

@@ -1,5 +1,8 @@
 const { getInventory } = require("./inventoryController");
 
+// This test _will_ fail.
+// Here I'm trying to demonstrate Jest's output
+// when an assertion like `.toBe(true)` fails.
 test("generatedAt in the past", () => {
   const result = getInventory();
   const currentTime = Date.now() + 1;