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Unit test fails with zone application and vitest #32555
Description
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
Hello Angular Team,
ng version: 21.1.5
Unit tests fail in a very weird way for projects that use the zone
Some fields of the components are simply not assigned, which causes a failure when the view is rendered
Strangely, this happens when multiples components consumes the same import ( this typically happens with exported constants )
You can find a simple repro below.
https://stackblitz.com/edit/angular-v21-starter-w7aywxrw?file=README.md
If I remove the polyfill, it passes ( I've noticed that the generated javascript is different )
Please not that we cannot migrate all our apps/libs to zoneless in one shot ( we are in an enterprise setup with a lot of libs ),
so it's really an issue that prevent us for migrating to ng21
Thanks for considering this issue,
FC
Minimal Reproduction
https://stackblitz.com/edit/angular-v21-starter-w7aywxrw?file=README.md
Exception or Error
Some fields of the component is undefined, which causes failure when the template is rendered during the test.
TypeError: Cannot read properties of undefined (reading 'A')
Your Environment
_ _ ____ _ ___
/ \ _ __ __ _ _ _| | __ _ _ __ / ___| | |_ _|
/ △ \ | '_ \ / _` | | | | |/ _` | '__| | | | | | |
/ ___ \| | | | (_| | |_| | | (_| | | | |___| |___ | |
/_/ \_\_| |_|\__, |\__,_|_|\__,_|_| \____|_____|___|
|___/
Angular CLI : 21.1.5
Angular : 21.1.5
Node.js : 20.19.1
Package Manager : npm 10.8.2
Operating System : linux x64
┌───────────────────────────┬───────────────────┬───────────────────┐
│ Package │ Installed Version │ Requested Version │
├───────────────────────────┼───────────────────┼───────────────────┤
│ @angular/build │ 21.1.5 │ ^21.1.5 │
│ @angular/cli │ 21.1.5 │ ^21.1.5 │
│ @angular/common │ 21.1.5 │ ^21.1.5 │
│ @angular/compiler │ 21.1.5 │ ^21.1.5 │
│ @angular/compiler-cli │ 21.1.5 │ ^21.1.5 │
│ @angular/core │ 21.1.5 │ ^21.1.5 │
│ @angular/forms │ 21.1.5 │ ^21.1.5 │
│ @angular/platform-browser │ 21.1.5 │ ^21.1.5 │
│ @angular/router │ 21.1.5 │ ^21.1.5 │
│ rxjs │ 7.8.2 │ ~7.8.0 │
│ typescript │ 5.9.3 │ ~5.9.2 │
│ vitest │ 4.0.18 │ ^4.0.8 │
│ zone.js │ 0.15.1 │ ~0.15.0 │
└───────────────────────────┴───────────────────┴──────────────────
Anything else relevant?
Removing the polyfill fixes it.
Tweaking the tsconfig.spec.json to use node module system fixes it ( see in the stackblitz )
Activity
JeanMeche commentedon Feb 24, 2026
I chatted with @chabb.
There is a race condition at play here. Here is what we found:
async/awaitthe test passes (code isn't downleveled anymore)chabb commentedon Feb 24, 2026
This looks like some kind of race condition, you can see the generate JS in the image below.
I've put a breakpoint, and it turns out than the TEST variable ( which is assigned to a field of the component and points to an export of a module ) is actually undefined. But the module itself has the right value, so I guess it has been defined at a later time
clydin commentedon Aug 13, 2026
Resolved via #33729
angular-automatic-lock-bot commentedon Oct 19, 2026
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