fix: Loosen up global XHR native check

packages/@pollyjs/adapter-fetch/src/index.js

@@ -2,7 +2,7 @@ import Adapter from '@pollyjs/adapter';
 import { Fetch as FetchUtils } from '@pollyjs/utils';
 
 const { defineProperty } = Object;
-const STUB_META = Symbol();
+const IS_STUBBED = Symbol();
 
 export default class FetchAdapter extends Adapter {
   static get name() {
@@ -22,7 +22,7 @@ export default class FetchAdapter extends Adapter {
     this.assert('Response global not found.', !!(context && context.Response));
     this.assert(
       'Running concurrent fetch adapters is unsupported, stop any running Polly instances.',
-      !(STUB_META in context.fetch)
+      !context.fetch[IS_STUBBED]
     );
 
     this.native = context.fetch;
@@ -36,7 +36,7 @@ export default class FetchAdapter extends Adapter {
         requestArguments: [url, options]
       });
 
-    defineProperty(context.fetch, STUB_META, { value: true });
+    defineProperty(context.fetch, IS_STUBBED, { value: true });
   }
 
   onDisconnect() {

packages/@pollyjs/adapter-xhr/src/index.js

@@ -1,9 +1,10 @@
 import FakeXHR from 'nise/lib/fake-xhr';
 import Adapter from '@pollyjs/adapter';
-import { XHR as XHRUtils } from '@pollyjs/utils';
 import resolveXhr from './utils/resolve-xhr';
+import { XHR as XHRUtils } from '@pollyjs/utils';
 
 const SEND = Symbol();
+const IS_STUBBED = Symbol();
 
 export default class XHRAdapter extends Adapter {
   static get name() {
@@ -14,10 +15,10 @@ export default class XHRAdapter extends Adapter {
     this.assert('XHR global not found.', FakeXHR.xhr.supportsXHR);
     this.assert(
       'Running concurrent XHR adapters is unsupported, stop any running Polly instances.',
-      global.XMLHttpRequest === FakeXHR.xhr.GlobalXMLHttpRequest
+      !global.XMLHttpRequest[IS_STUBBED]
     );
 
-    this.native = FakeXHR.xhr.GlobalXMLHttpRequest;
+    this.native = global.XMLHttpRequest;
     this.xhr = FakeXHR.useFakeXMLHttpRequest();
 
     this.xhr.onCreate = xhr => {
@@ -31,9 +32,12 @@ export default class XHRAdapter extends Adapter {
           body
         });
     };
+
+    global.XMLHttpRequest[IS_STUBBED] = true;
   }
 
   onDisconnect() {
+    delete global.XMLHttpRequest[IS_STUBBED];
     this.xhr.restore();
   }
 

packages/@pollyjs/adapter-xhr/tests/integration/adapter-test.js

@@ -1,4 +1,4 @@
-import { setupMocha as setupPolly } from '@pollyjs/core';
+import { Polly, setupMocha as setupPolly } from '@pollyjs/core';
 import setupFetchRecord from '@pollyjs-tests/helpers/setup-fetch-record';
 import adapterTests from '@pollyjs-tests/integration/adapter-tests';
 import adapterBrowserTests from '@pollyjs-tests/integration/adapter-browser-tests';
@@ -26,3 +26,34 @@ describe('Integration | XHR Adapter', function() {
   adapterTests();
   adapterBrowserTests();
 });
+
+describe('Integration | XHR Adapter | Concurrency', function() {
+  it('should prevent concurrent XHR adapter instances', async function() {
+    const one = new Polly('one');
+    const two = new Polly('two');
+
+    one.connectTo(XHRAdapter);
+
+    expect(function() {
+      two.connectTo(XHRAdapter);
+    }).to.throw(/Running concurrent XHR adapters is unsupported/);
+
+    await one.stop();
+    await two.stop();
+  });
+
+  it('should allow you to register new instances once stopped', async function() {
+    const one = new Polly('one');
+    const two = new Polly('two');
+
+    one.connectTo(XHRAdapter);
+    await one.stop();
+
+    expect(function() {
+      two.connectTo(XHRAdapter);
+    }).to.not.throw();
+
+    await one.stop();
+    await two.stop();
+  });
+});