try waiting until requests to the tunnel work

jest.config.appscript.ts

@@ -9,7 +9,7 @@ export default {
   rootDir: 'tests/appscript',
   preset: 'ts-jest/presets/js-with-ts-esm',
   testEnvironment: 'node',
-  testTimeout: 180000,
+  testTimeout: 300000,
   globalSetup: '../globalSetup.js',
   globalTeardown: '../globalTeardown.js',
   maxWorkers: 1, // since we run our tests within apps script, we can't run them in parallel

tests/appscript/api.spec.ts

@@ -8,6 +8,7 @@
 import { beforeEach, beforeAll, expect } from '@jest/globals';
 import Clasp from '../utilities/clasp';
 import { makeApiFailureMockServer } from './api/mockServer';
+import axios from 'axios';
 
 describe('api', () => {
   let server: ReturnType<typeof makeApiFailureMockServer>;
@@ -47,6 +48,26 @@ describe('api', () => {
     });
   }
 
+  async function waitForMockServer() {
+    const testUrl = `${tunnel.url}/index.php`;
+    const body = {
+      method: 'SitesManager.getSitesIdWithAtLeastViewAccess',
+    };
+
+    while (true) {
+      await new Promise((resolve) => setTimeout(resolve, 2000));
+
+      try {
+        const response = await axios.post(testUrl, body);
+        if (Array.isArray(response.data) && response.data[0] === 1) {
+          return;
+        }
+      } catch (e) {
+        // retry
+      }
+    }
+  }
+
   describe('extractBasicAuthFromUrl()', () => {
     const URLS_WITHOUT_CREDENTIALS = [
       'http://mymatomo.com/',
@@ -129,7 +150,7 @@ describe('api', () => {
         },
       });
 
-      await new Promise((resolve) => setTimeout(resolve, 10000));
+      await waitForMockServer();
 
       // use the mock server's path that forces a random error
       const result = await Clasp.run('setCredentials', {
@@ -175,7 +196,7 @@ describe('api', () => {
       });
 
       // waiting seems to be required here, or the mock server isn't used in time
-      await new Promise((resolve) => setTimeout(resolve, 10000));
+      await waitForMockServer();
 
       // use the mock server's path that forces a non-random error
       await Clasp.run('setCredentials', {
@@ -218,7 +239,7 @@ describe('api', () => {
         },
       });
 
-      await new Promise((resolve) => setTimeout(resolve, 10000));
+      await waitForMockServer();
 
       // use the mock server's path that forces a non-random error
       await Clasp.run('setCredentials', {