Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

v20.2.2

Description

Hello, I updated my project where I use material from angular version 20.2.2 to version 21.0.5. After updating Angular I configured it to work with Vitest when i run ng test. It all works fine except when I do the following line const loader = TestbedHarnessEnvironment.loader(fixture); in my tests.

When that line is in my spec file and I run ng test I get the error Error: Expected to be running in 'ProxyZone', but it was not found..

How can I solve this so my tests that use TestbedHarnessEnvironment.loader will run again?

Reproduction

I tried to make a stackblitz, but wasn't able to get ng serve with vitest to work.

StackBlitz link: https://stackblitz.com/edit/stackblitz-starters-peyuzeyh?file=src%2Fapp%2Fapp.component.spec.ts
Steps to reproduce:

1. Install angular 21
2. Install Material
3. npm i -D vitest jsdom
4. configure test in angular.json
5. Add mat-form-field to html of component
6. Add spec file to component that uses TestbedHarnessEnvironment.loader
7. Run ng test

Expected Behavior

Test should work, not throw error and pass

Actual Behavior

ng test throws error: Error: Expected to be running in 'ProxyZone', but it was not found.

Environment

• Angular: 21.0.5
• CDK/Material: 21.0.3
• Browser(s): Chrome
• Operating System: Windows