Angular 21 new unit test builder with Karma and zone.js

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#32,905 3 comments 4 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
angular, typescript
Domain
build-system, testing

Research direction

Start with packages/angular/build/src/builders/unit-test/runners/karma/executor.ts and compare the Angular 20 and 21 unit-test builder configuration in angular.json. Read the testing migration documentation linked in the report and trace how Karma handles global test setup. Done means the expected Karma configuration is established and the documentation or migration behavior addresses the reported upgrade path.

Written by the indexing model from the issue text.

Description

area: @angular/cli gemini-triaged
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

20

Description

After upgrading from Angular 20 to 21, I ran into NGXXXX errors when running unit tests still with Karma and zone.js.
I found a closed issue and a supposed fix for it, but that did not resolve the issue.
Others experienced the same and implemented workarounds which actually do work: StackOverflow, Reddit.

I found that the solution could be that the angular.json has to be modified to be in line with the new project template like this:

  • change "builder": "@angular/build:karma" to "builder": "@angular/build:unit-test"
  • add "runner": "karma"
  • remove the rest of the properties (according to documentation these derive from the development configuration)

I did not find anything regarding the necessity of this change in the documentation, but if that is the case, it would be wise to mention it and maybe even add a migration schematic.

Also its not clear what is the alternative for "main": "src/test.ts" which contains global test setup. My guess is that the "setupFiles" property would be the successor (like "karmaConfig" became "runnerConfig"), but that is disabled for Karma.

So my question is: Where should I put global test setup with the new "unit-test" builder when using Karma?

Thanks in advance.

Minimal Reproduction

npm test

Exception or Error
Your Environment
Angular CLI       : 21.2.5
Node.js           : 24.14.0
Package Manager   : npm 11.9.0
Operating System  : win32 x64
Anything else relevant?

No response

Dominant language
TypeScript
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