Performance Improvements (similiar ng-bullet)

[r-kernberger]

Performance Improvements (similiar ng-bullet)

Feature Request

A large Unit Test (23 Tests) is running for ~10minutes.
There is a library (ng-bullet), which avoids recompiling everything
used to configure the TestBed for every test in a suite, thus increasing the overall test execution time alot (~30 seconds).
https://github.com/topnotch48/ng-bullet-workspace/blob/master/projects/ng-bullet/README.md

Downside on this library is, that it is no longer maintained.
Are there any plans, integrating the approach of ng-bullet
in jest in the near future and thus increasing the performance of jest?

To Reproduce

• Writing a unit test with > 20 Tests.
• Execute the test and measure execution time
• Install ng-bullet
• Execute the same test and measure execution time again
• Compare Execution times

Expected behavior

Execution time of Jest unit tests will be similiar to execution time when using ng-bullet

Link to repl or repo (highly encouraged)

envinfo

System:
OS: Windows 10 10.0.17763
CPU: (12) x64 Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
Binaries:
Node: 10.15.0 - C:\Program Files\nodejs\node.EXE
npm: 6.4.1 - C:\Program Files\nodejs\npm.CMD

[ahnpnl]

definitely, I think it looks very promising.

[wtho]

In the root README of the linked repository the owner recommends another project, maybe we should consider both.
Referenced project.

[splincode]

Not mantained
https://github.com/topnotch48/ng-bullet-workspace#update

[ahnpnl]

Look at spectator, it seems to be out of the scope of the preset. Not sure how to integrate into here.

[r-kernberger]

Not mantained
https://github.com/topnotch48/ng-bullet-workspace#update

@splincode
That was the whole point of this feature request. ng-bullet is not maintained, so it would be great if "jest-preset-angular" would integrate the performance boost of ng-bullet.

[wtho]

@r-kernberger I see.
We currently have other features in focus, but we are always open to PRs.

I think key for success of this integration is that the interface of the tests does not change (much), so that developers have a low threshold to adopt the performance boost.

E. g. this could be an integration I would love:

  import {
    async,
    ComponentFixture,
-   TestBed
  } from '@angular/core/testing';
+ import { TestBed } from 'jest-preset-angular/speedup-testbed';

  describe('suite', () => {
    let comp, userService;
    beforeEach(() => {
      TestBed.configureTestingModule({
        providers: [ WelcomeComponent, { provide: UserService, useClass: MockUserService } ]
      });
      comp = TestBed.inject(WelcomeComponent);
      userService = TestBed.inject(UserService);
    });

    it('should not have welcome message after construction', () => {
      expect(comp.welcome).toBeUndefined();
    });
  });