Cannot set base providers because it has already been called when running >1 test cases with Vitest ^4.0.5

Which @angular/* package(s) are the source of the bug?

Don't known / other

Is this a regression?

Yes

Description

When running an Angular test suite with @angular/platform-browser/testing@21.2.1 and vitest@4.0.18, the test runner throws the following error after the second test case:

Error: Cannot set base providers because it has already been called
The error originates from Angular's TestBed.initTestEnvironment() being invoked multiple times within the same worker context. Vitest ^4.0.5 appears to have changed how setupFiles and worker isolation interact, causing the test-setup.ts to be re-executed for subsequent test files while the Angular TestBed state is already initialized from the previous run.

The issue only surfaces when running 2 or more test files/cases on Github Actions. Running 1 passes without error.

Please provide a link to a minimal reproduction of the bug

No response

Please provide the exception or error you saw

Error: Cannot set base providers because it has already been called
   ❯ _TestBedImpl.initTestEnvironment ../../node_modules/.pnpm/k8-fastbuild-ST-fdfa778d11ba/bin/packages/core/testing/src/test_bed.ts:477:13
   ❯ ../../test-setup.ts:145:14
      143| );
      144| 
      145| getTestBed().initTestEnvironment(
         |              ^
      146|   BrowserTestingModule,
      147|   platformBrowserTesting(),

Please provide the environment you discovered this bug in (run `ng version`)

vitest	4.0.18
@vitest/coverage-v8	4.0.18
@analogjs/vitest-angular	2.2.1
@analogjs/vite-plugin-angular	^2.3.1
@angular/core	21.2.1
@nx/vitest	22.5.4
happy-dom	^20.1.0
typescript	5.9.3
@angular/platform-browser	21.2.1
@angular/core	21.2.1

Anything else?

This issue is reported in the vitest repository, they implied that "Angular forces isolate to be false.", which cause the issue
[https://github.com/vitest-dev/vitest/issues/8944](Regression: 4.0.5 broke Angular tests’ isolation?)

This issue is reported in the vitest repository, they implied that "Angular forces isolate to be false.",

The integrated Vitest support via the unit-test builder system defaults isolation to false but it can be configured via a Vitest configuration file if needed/preferred.

However, from the package list above (specifically, @analogjs/vitest-angular), it appears the project may not be using the Angular build system's Vitest integration. If so, this is either an issue with the aforementioned package or a project configuration concern. Please consider opening an issue with AnalogJS if this is the case as it is a third-party package which is not directly supported by the Angular team. If not, please provide the relevant test target within the project's angular.json file.

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Cannot set base providers because it has already been called when running >1 test cases with Vitest ^4.0.5 #32754

Which @angular/* package(s) are the source of the bug?

Is this a regression?

Description

Please provide a link to a minimal reproduction of the bug

Please provide the exception or error you saw

Please provide the environment you discovered this bug in (run `ng version`)

Anything else?

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Cannot set base providers because it has already been called when running >1 test cases with Vitest ^4.0.5 #32754

Description

Which @angular/* package(s) are the source of the bug?

Is this a regression?

Description

Please provide a link to a minimal reproduction of the bug

Please provide the exception or error you saw

Please provide the environment you discovered this bug in (run ng version)

Anything else?

Activity

clydin commented on Mar 12, 2026

alan-agius4 commented on Mar 19, 2026

angular-automatic-lock-bot commented on Apr 19, 2026

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Please provide the environment you discovered this bug in (run `ng version`)