Angular-builders: "polyfills.ts not found" in angular 8 project

[snebjorn]

Describe the bug
When running ng test every test suite will fail with this message:

Test suite failed to run

TypeScript diagnostics (customize using [jest-config].globals.ts-jest.diagnostics option):
error TS6053: File 'myprojectroot/polyfills.ts' not found.

To Reproduce
Steps to reproduce the behavior:

1. Run ng new foo
2. Add @angular-builders/jest
3. Write a test
4. Run ng test
5. See error

Expected behavior
Tests should run

Builder:

• @angular-builders/jest
• 8.0.2

Libraries

• angular-devkit/build-angular: 0.800.2

Additional context
I think the problem is that it's assumed that polyfill.ts was moved to the root dir. It was not.
A newly created angular project have the following config

"polyfills": "src/polyfills.ts",

[just-jeb]

Are you sure this problem reproduces when you follow the documentation? Because here are two example apps (one for single project, second for multi-project) and they both work fine...

[snebjorn]

Oops, the problem was a configuration.

Had this in my tsconfig.spec.json file

"files": ["polyfills.ts"],

Should be

"files": ["src/polyfills.ts"],