Angular 8+ tsconfig Path Aliases not Recognized in .spec files

Question

I am working on some Angular testing and my spec files will not recognize my paths and they give me a red squiggle import warning in VS Code (and show up in Problems) despite the fact that they work in every other way (testing works, etc.). I am assuming this is a tsconfig issue and not a linting issue as the error it gives me is: Cannot find module '@feature/<reference path>.<file type>'.ts(2307)

It functionally doesn't affect me much, but it is annoying (and kills automatic imports).

tsconfig.json:

{
    "compileOnSave": false,
    "compilerOptions": {
        "module": "esnext",
        "outDir": "./dist/out-tsc",
        "strictNullChecks": true,
        "noImplicitAny": false,
        "noImplicitThis": true,
        "alwaysStrict": false,
        "forceConsistentCasingInFileNames": true,
        "noImplicitReturns": true,
        "noUnusedLocals": true,
        "skipLibCheck": true,
        "sourceMap": true,
        "declaration": false,
        "moduleResolution": "node",
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "allowJs": true,
        "resolveJsonModule": true,
        "esModuleInterop": true,
        "target": "es2015",
        "types": [
            "node",
            "arcgis-js-api",
            "jest"
        ],
        "typeRoots": [
            "node_modules/@types"
        ],
        "lib": [
            "es2017",
            "dom",
            "esnext.asynciterable"
        ],
        "baseUrl": ".",
        "paths": {
            "core-js/es6/*": [
                "node_modules/core-js/es/*"
            ],
            "core-js/es7/reflect": [
                "node_modules/core-js/proposals/reflect-metadata"
            ],
            "@core/*": [
                "src/app/core/*"
            ],
            "@shared/*": [
                "src/app/shared/*"
            ],
            "@feature/*": [
                "src/app/feature/*"
            ],
            "@test/*": [
                "src/test/*"
            ],
            "@/*": [
                "src/*"
            ]
        }
    },
    "files": [
        "src/main.ts",
        "src/polyfills.ts"
    ],
    "include": [
        "**/*.d.ts"
    ]
}

tsconfig.spec.json and tsconfig.app.json paths (note standard folder structure from angular-cli):

{
    "extends": "../tsconfig.json",
    "compilerOptions": {
        "outDir": "../out-tsc/spec"
    }
}

angular.json

...
            "test": {
                "builder": "@angular-builders/jest:run",
                "options": {
                    "tsConfig": "src/tsconfig.spec.json",
                    "no-cache": true,
                    "polyfills": "src/polyfills.ts",
                    "configPath": "./jest.config.js",
                    "styles": [
                        "node_modules/font-awesome/css/font-awesome.css",
                        "src/styles.scss"
                    ],
                    "scripts": [],
                    "assets": [
                        "src/favicon.ico",
                        "src/assets",
                        "src/manifest.json",
                    ],
                    "stylePreprocessorOptions": {
                        "includePaths": [
                            "src"
                        ]
                    }
                }
            },
            "lint": {
                "builder": "@angular-devkit/build-angular:tslint",
                "options": {
                    "tsConfig": [
                        "src/tsconfig.app.json",
                        "src/tsconfig.spec.json"
                    ],
                    "exclude": [
                        "**/node_modules/**"
                    ]
                }
            }
...

Versions:

Angular CLI: 8.3.6
Node: 12.3.1
OS: win32 x64
Angular: 8.2.8
... animations, common, compiler, compiler-cli, core, forms     
... language-service, platform-browser, platform-browser-dynamic
... router, service-worker

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.803.6
@angular-devkit/build-angular     0.803.6
@angular-devkit/build-optimizer   0.803.6
@angular-devkit/build-webpack     0.803.6
@angular-devkit/core              8.3.6
@angular-devkit/schematics        8.3.6
@angular/cli                      8.3.6
@angular/pwa                      0.803.6
@ngtools/webpack                  8.3.6
@schematics/angular               8.3.6
@schematics/update                0.803.6
rxjs                              6.5.3
typescript                        3.5.3
webpack                           4.39.2

Answer 1

In my case, I forgot to setup jest.config.js file according of my project.

tsconfig.ts
...
"@app/*": ["src/app/*"],
...

and

jest.config.js

module.exports = {
    moduleNameMapper: {
        "@app/(.*)$": "<rootDir>/src/app/$1"
    } 
};

Reference: https://jestjs.io/docs/en/configuration#modulenamemapper-objectstring-string--arraystring

Answer 2

tsconfig.ts

{
  "compilerOptions": {
    ....
    "paths": {
      "@app1/*" : ["src/*"]
    }
  }
}

packages.json

  "jest": {
    ...
    "rootDir": "src",
    "moduleNameMapper": {
      "@app1/(.*)$": "<rootDir>/$1"
    } 
  }