Regression: 4.0.5 broke Angular tests’ isolation?

[arty-name]

Describe the bug

My Angular project uses Vite and Vitest.

After a recent upgrade from 4.0.4 to 4.0.5 the tests started failing with errors:

On a test level in configureTestingModule:

Cannot configure the test module when the test module has already been instantiated. Make sure you are not using inject before TestBed.configureTestingModule

On a suite level in initTestEnvironment:

Cannot set base providers because it has already been called

Reproduction

https://github.com/arty-name/vitest-repro

System Info

System:
    OS: Linux 6.14 Ubuntu 25.04 25.04 (Plucky Puffin)
    CPU: (8) x64 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
    Memory: 11.53 GB / 30.63 GB
    Container: Yes
    Shell: 4.0.1 - /usr/bin/fish
  Binaries:
    Node: 24.11.0 - /usr/bin/node
    Yarn: 1.22.19 - /usr/bin/yarn
    npm: 11.6.1 - /usr/bin/npm
    pnpm: 10.19.0 - /usr/bin/pnpm
  Browsers:
    Chrome: 142.0.7444.59
    Firefox: 144.0.2
    Firefox Developer Edition: 144.0.2
  npmPackages:
    @vitest/coverage-v8: ^4.0.5 => 4.0.5 
    @vitest/ui: ^4.0.5 => 4.0.5 
    vitest: ^4.0.5 => 4.0.5

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[arty-name]

The minimal reproduction unfortunately cannot be run on StackBlitz.

I could not showcase clearly that with 4.0.4 I could run configureTestingModule in beforeEach, not beforeAll. To see the configureTestingModule error, change beforeAll to beforeEach.

The error only shows up with maxWorkers: 1, which is how our CI runs the tests.

[axelforsti]

I have the same issue after upgrading from vitest v3 to v4 - very confusing as well because the tests work locally but fail in CI (because maxWorkers is 1 there?)

[sheremet-va]

Vitest fixed a bug that was causing the environment to be recreated if isolate was disabled. Vitest works as expected, if there is an issue with Angular integrations, please open an issue in their repo: https://github.com/angular/angular/issues?q=sort%3Aupdated-desc+is%3Aissue+is%3Aopen

[arty-name]

@sheremet-va, isolate: true doesn’t fix the bug. In fact, we didn’t have isolate: false.

[sheremet-va]

@sheremet-va, isolate: true doesn’t fix the bug. In fact, we didn’t have isolate: false.

Angular forces isolate to be false.