TestBed.overrideComponent doesn't work with AOT and webpack

Start with the minimal reproduction: a component test using TestBed.overrideComponent or TestBed.overrideModule with Karma, the webpack builder in browser mode, and AOT enabled. Compare the failure with application builder mode or AOT disabled, then verify that the override test runs without the missing @Component metadata error under the affected configuration.

Command

test

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

No response

Description

TestBed.overrideComponent and TestBed.overrideModule don't seem to work with karma, webpack builder (builderMode: browser) and aot enabled. Changing any of these settings, so builderMode: application or disabling aot "fixes" the problem. The same issue was reported here https://github.com/angular/angular-cli/issues/30017 but i guess it was only fixed for esbuild? Is there any workaround for this? or can it be fixed for angular20?

Minimal Reproduction

Create a simple valid component, turn on AOT for Karma, and make a test where you use TestBed.overrideComponent to reset metadata. You don't even need to specify an actual override in the second parameter to trigger the issue: TestBed.overrideComponent(YourComponent, {}) triggers the failure.

builderMode: browser needs to be set

Exception or Error

Error: App class doesn't have @Component decorator or is missing metadata.
            at invalidTypeError (node_modules/@angular/core/fesm2022/testing.mjs:1661:12)
            at forEach (node_modules/@angular/core/fesm2022/testing.mjs:1084:23)
            at asyncGeneratorStep (node_modules/@babel/runtime/helpers/esm/asyncToGenerator.js:3:1)
            at apply (node_modules/@babel/runtime/helpers/esm/asyncToGenerator.js:17:1)
            at _ZoneDelegate.invoke (node_modules/zone.js/fesm2015/zone.js:398:28)
            at ProxyZoneSpec.onInvoke (node_modules/zone.js/fesm2015/zone-testing.js:2132:39)

Your Environment

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    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/
    


Angular CLI: 20.3.18
Node: 22.22.0
Package Manager: npm 10.9.4
OS: win32 x64


Angular: 20.3.17
... common, compiler, compiler-cli, core, forms
... platform-browser, router

Package                         Version
---------------------------------------
@angular-devkit/architect       0.2003.18
@angular-devkit/build-angular   20.3.16
@angular-devkit/core            20.3.18
@angular-devkit/schematics      20.3.18
@angular/build                  20.3.18
@angular/cli                    20.3.18
@schematics/angular             20.3.18
rxjs                            7.8.2
typescript                      5.9.3
zone.js                         0.15.1

Anything else relevant?

No response