Enforce using fetch in tests

test/util.ts

@@ -1,5 +1,5 @@
 import { readFileSync } from "fs";
-import { DNSimple } from "../lib/main";
+import { DNSimple, TimeoutError } from "../lib/main";
 
 function hasJsonContent(lines: string[]) {
   for (let line of lines) {
@@ -29,6 +29,29 @@ function parseBody(lines: string[]) {
 export function createTestClient() {
   return new DNSimple({
     accessToken: process.env["TOKEN"] ?? "bogus",
+    fetcher: async (params: {
+      method: string;
+      url: string;
+      headers: { [name: string]: string };
+      timeout: number;
+      body?: string;
+    }) => {
+      const abortController = new AbortController();
+      setTimeout(() => abortController.abort(), DNSimple.DEFAULT_TIMEOUT);
+      try {
+        const response = await fetch(params.url, {
+          method: params.method,
+          headers: params.headers,
+          body: params.body,
+          signal: abortController.signal,
+        });
+        return { status: response.status, body: await response.text() };
+      } catch (error) {
+        if (abortController && abortController.signal.aborted) throw new TimeoutError();
+
+        throw error;
+      }
+    },
   });
 }