Bug 1800545 - Start a http server in test_ext_proxy_config.js, r=robwu

Differential Revision: https://phabricator.services.mozilla.com/D162042

toolkit/components/extensions/test/xpcshell/test_ext_proxy_config.js

@@ -20,6 +20,11 @@ AddonTestUtils.createAppInfo(
   "42"
 );
 
+// Start a server for `pac.example.com` to intercept attempts to connect to it
+// to load a PAC URL. We won't serve anything, but this prevents attempts at
+// non-local connections if this domain is registered.
+AddonTestUtils.createHttpServer({ hosts: ["pac.example.com"] });
+
 add_task(async function setup() {
   // Bug 1646182: Force ExtensionPermissions to run in rkv mode, the legacy
   // storage mode will run in xpcshell-legacy-ep.ini
@@ -188,11 +193,11 @@ add_task(async function test_browser_settings() {
   await testProxy(
     {
       proxyType: "autoConfig",
-      autoConfigUrl: "http://mozilla.org",
+      autoConfigUrl: "http://pac.example.com",
     },
     {
       "network.proxy.type": proxySvc.PROXYCONFIG_PAC,
-      "network.proxy.autoconfig_url": "http://mozilla.org",
+      "network.proxy.autoconfig_url": "http://pac.example.com",
       "network.http.proxy.respect-be-conservative": true,
     }
   );