fix: harnesses not working on Stackblitz (#1193)

Updates the test.ts to use the correct API for discovering the test files.

Fixes angular/components#26806.

Author: crisbeto

src/assets/stack-blitz/src/test.ts

@@ -7,20 +7,17 @@ import {
   platformBrowserDynamicTesting
 } from '@angular/platform-browser-dynamic/testing';
 
-declare const require: {
-  context(path: string, deep?: boolean, filter?: RegExp): {
-    keys(): string[];
-    <T>(id: string): T;
-  };
-};
-
 // First, initialize the Angular testing environment.
 getTestBed().initTestEnvironment(
   BrowserDynamicTestingModule,
   platformBrowserDynamicTesting()
 );
 
 // Then we find all the tests.
-const context = require.context('./', true, /\.spec\.ts$/);
+const context = (import.meta as any).webpackContext('./', {
+  recursive: true,
+  regExp: /\.spec\.ts$/
+});
+
 // And load the modules.
 context.keys().map(context);