fix type error in stubbing example

examples/tutorials/stubbing.md

@@ -32,21 +32,23 @@ Here's a simple example demonstrating how to stub a function:
 import { assertEquals } from "jsr:@std/assert";
 import { stub } from "jsr:@std/testing/mock";
 
-// Original function
-function getUserName(id: number): string {
-  // In a real app, this might call a database
-  return "Original User";
-}
+// Wrap dependencies so they can be stubbed safely from tests.
+const deps = {
+  getUserName(_id: number): string {
+    // In a real app, this might call a database
+    return "Original User";
+  },
+};
 
 // Function under test
 function greetUser(id: number): string {
-  const name = getUserName(id);
+  const name = deps.getUserName(id);
   return `Hello, ${name}!`;
 }
 
 Deno.test("greetUser with stubbed getUserName", () => {
   // Create a stub that returns a controlled value
-  const getUserNameStub = stub(globalThis, "getUserName", () => "Test User");
+  const getUserNameStub = stub(deps, "getUserName", () => "Test User");
 
   try {
     // Test with the stubbed function
@@ -136,17 +138,21 @@ import { returnsNext, stub } from "jsr:@std/testing/mock";
 import { assertEquals } from "jsr:@std/assert";
 
 Deno.test("stub with multiple return values", () => {
+  const dataService = {
+    fetchData: () => "original data",
+  };
+
   const fetchDataStub = stub(
-    globalThis,
+    dataService,
     "fetchData",
     // Return these values in sequence
     returnsNext(["first result", "second result", "third result"]),
   );
 
   try {
-    assertEquals(fetchData(), "first result");
-    assertEquals(fetchData(), "second result");
-    assertEquals(fetchData(), "third result");
+    assertEquals(dataService.fetchData(), "first result");
+    assertEquals(dataService.fetchData(), "second result");
+    assertEquals(dataService.fetchData(), "third result");
   } finally {
     fetchDataStub.restore();
   }
@@ -165,8 +171,12 @@ Deno.test("stub with custom implementation", () => {
   // Create a counter to track how many times the stub is called
   let callCount = 0;
 
+  const mathService = {
+    calculate: (a: number, b: number) => a + b,
+  };
+
   const calculateStub = stub(
-    globalThis,
+    mathService,
     "calculate",
     (a: number, b: number) => {
       callCount++;
@@ -175,7 +185,7 @@ Deno.test("stub with custom implementation", () => {
   );
 
   try {
-    const result = calculate(5, 10);
+    const result = mathService.calculate(5, 10);
     assertEquals(result, 25); // 5 + (10 * 2)
     assertEquals(callCount, 1);
   } finally {
@@ -192,8 +202,12 @@ One of the most common uses of stubs is to replace API calls during testing:
 import { assertEquals } from "jsr:@std/assert";
 import { stub } from "jsr:@std/testing/mock";
 
+const apiClient = {
+  fetch: globalThis.fetch,
+};
+
 async function fetchUserData(id: string) {
-  const response = await fetch(`https://api.example.com/users/${id}`);
+  const response = await apiClient.fetch(`https://api.example.com/users/${id}`);
   if (!response.ok) {
     throw new Error(`Failed to fetch user: ${response.status}`);
   }
@@ -206,9 +220,9 @@ Deno.test("fetchUserData with stubbed fetch", async () => {
     { status: 200, headers: { "Content-Type": "application/json" } },
   );
 
-  // Replace global fetch with a stubbed version
+  // Replace apiClient.fetch with a stubbed version
   const fetchStub = stub(
-    globalThis,
+    apiClient,
     "fetch",
     () => Promise.resolve(mockResponse),
   );