Vitest: Code coverage of html file incorrect when using overridecomponent

[paulstelzer]

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

Code coverage with vitest in html drops to 0 percent when using overridecomponent. This is a valid test pattern to only unit test this component (https://angular.dev/guide/testing/components-scenarios#nested-component-tests).

The code coverage should still be 100%.

Minimal Reproduction

ng new <project-name> (with vitest unit test)

Update angular.json to include code coverage

        "test": {
          "builder": "@angular/build:unit-test",
          "options": {
            "coverage": true
          }
        }

ng test

Code coverage of the app.html is 100%:

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	100	91.66	100	100
app.html	100	100	100	100
app.ts	100	91.66	100	100	11
----------	---------	----------	---------	---------	-------------------

If you now update the app.spec.ts to:

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [App],
    }).overrideComponent(App, {
      set: {
        imports: [],
        schemas: [NO_ERRORS_SCHEMA]
      }
    }).compileComponents();
  });

app.html statements coverage drops to 0 percent.

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	9.09	58.33	14.28	4.54
app.html	0	100	0	0	185-342
app.ts	83.33	58.33	100	100	10-11
----------	---------	----------	---------	---------	-------------------

Exception or Error

Your Environment

Angular CLI       : 21.1.4
Angular           : 21.1.4
Node.js           : 24.5.0
Package Manager   : npm 11.5.1
Operating System  : darwin arm64

Anything else relevant?

No response

[JoostK]

This is a duplicate of #30127. By default, the Vitest runner uses the regular build target which has AOT enabled.