feat: add doNotUseFetch helper to the test utils

v-next/hardhat-test-utils/src/global.ts

@@ -0,0 +1,16 @@
+import { after, before } from "node:test";
+
+export function doNotUseFetch(): void {
+  let originalFetch: typeof global.fetch;
+
+  before(async () => {
+    originalFetch = global.fetch;
+    global.fetch = async () => {
+      throw new Error("Network requests are disabled");
+    };
+  });
+
+  after(async () => {
+    global.fetch = originalFetch;
+  });
+}

v-next/hardhat-test-utils/src/index.ts

@@ -1,3 +1,4 @@
 export * from "./fixture-projects.js";
-export * from "./hardhat-error.js";
 export * from "./fs.js";
+export * from "./global.js";
+export * from "./hardhat-error.js";