Jasmine to Jest: Adapted from https://dev.to/dylanwatsonsoftware/make-your-angular-tests-1000-faster-by-switching-from-karma-to-jest-1n33

check-progress.js

var glob = require("glob")

Reset = "\x1b[0m"
FgRed = "\x1b[31m"
FgGreen = "\x1b[32m"
FgYellow = "\x1b[33m"
FgWhite = "\x1b[37m"

let specs = glob.sync("src/**/*.spec.ts");
let tests = glob.sync("src/**/*.test.ts");

console.log(FgYellow, `${specs.join('\n')}`, Reset)

if (specs.length) {
  console.log(FgRed, specs.length + " slow karma tests")
} else {
  console.log(FgGreen, 'Wooooooooooooooooooooo! Jest conversion complete!')
}
console.log(FgWhite, tests.length + " fast jest tests")
console.log(FgGreen, (tests.length * 100 / (tests.length + specs.length)).toFixed(2) + "% complete in switching tests to jest", Reset)

convert-to-jest.js

var fs = require('fs')
var filename = process.argv[2]

if (!filename) {
  let specs = require('glob').sync("src/**/*.spec.ts");
  for (spec of specs) {
    if (!spec.includes('pact')) {
      convertToJest(spec);
    }
  }
} else {
  convertToJest(filename);
}

function convertToJest(filename) {
  if (!filename.startsWith('C:')) {
    filename = './' + filename
  }

  fs.readFile(filename, 'utf8', function (err, data) {
    if (err) {
      return console.log(err);
    }
    var result = data;
    // result = result.replace(' } from \'@ngneat/spectator\';', ', SpyObject } from \'@ngneat/spectator/jest\';');
    // result = result.replace('} from \'@ngneat/spectator\';', ', SpyObject } from \'@ngneat/spectator/jest\';');
    result = result.replace(/\.and\.returnValue/g, '.mockReturnValue');
    result = result.replace(/\.spec\'/g, '.test');
    // result = result.replace(/jasmine\.SpyObj/g, 'SpyObj');
    result = result.replace(/spyOn/g, 'jest.spyOn');
    result = result.replace(/spyOnProperty/g, 'spyOn');
    result = result.replace(/expect\((.*)\.calls\.first\(\)\.args\)\.toEqual\(\[(.*)\]\);/g, 'expect($1).toHaveBeenCalledWith($2);')
    result = result.replace(/expect\((.*)\.calls\.any\(\)\)\.toBe\((.*)\);/g, 'expect($1).toHaveBeenCalledWith($2);');
    result = result.replace(/expect\((.*)\.calls\.mostRecent\(\)(\.args\[.*\])?\)\.toEqual\((.*)\);/g, 'expect($1).toHaveBeenCalledWith($2);');
    result = result.replace(/expect\((.*)\.calls\.count\(\)\)\.toBe\((.*)\);/g, 'expect($1).toHaveBeenCalledTimes($2);');
    result = result.replace(/expect\((.*)\.calls\.count\(\)\)\.toEqual\((.*)\);/g, 'expect($1).toHaveBeenCalledTimes($2);');
    result = result.replace(/\.calls\.first\(\).args\[(\d+)\]/g, '.mock.calls[0][$1]');
    result = result.replace(/\.calls\.first\(\).args/g, '.mock.calls[0].args');
    result = result.replace(/.and.callFake/g, '.mockImplementation');
    result = result.replace(/.and.callThrough\(\);/g, ';');
    result = result.replace(/(.*).calls\.reset\(\);/g, '$1.mockClear();');

    result = result.replace(/jasmine.createSpyObj\(/g, 'createSpyObj(');
    result = result.replace(/jasmine.createSpy\(\'(.*)\'\);/g, 'jest.fn();');
    // result = result.replace(/createService\(/g, 'createServiceFactory(');
    // result = result.replace(/createService,/g, 'createServiceFactory,');

    if (result.includes('createSpyObj')) {
      result = 'import { createSpyObj } from \'src/testing/createSpy\';\r\n' + result;
    }
    if (result.includes('jasmine.clock().mockDate')) {
      result = 'import { advanceBy, advanceTo, clear } from \'jest-date-mock\';\r\n' + result;
    }

    // result = result.replace('import SpyObj = SpyObj;', '');
    // result = result.replace('import Spy = jasmine.Spy;', '');
    // result = result.replace('import createSpyObj = createSpyObj;', '');
    result = result.replace('import { configureTestSuite } from \'ng-bullet\';', 'import { configureTestSuite } from \'src/testing/jest-bullet\';');

    // result = result.replace(/ Spy;/g, ' jest.SpyInstance;');
    result = result.replace(/: jasmine.SpyObj</g, ': jest.Mocked<');
    result = result.replace(/: jasmine\.Spy</g, ': jest.MockedFunction<');
    result = result.replace(/: jasmine\.Spy/g, ': jest.Mock');

    // result = result.replace(/configureTestSuite\(\(\)\s*=\>\s*\{(.*?)\}\);/s, 'beforeEach(async(() => {$1}));');

    result = result.replace(/(\s)it\(\'/g, '$1test(\'');
    result = result.replace(/(\s)it\(\`/g, '$1test(\`');

    result = result.replace(/.innerText/g, '.textContent.trim()');

    result = result.replace(/jasmine.clock\(\).install\(\)/g, 'jest.useFakeTimers()');
    result = result.replace(/jasmine.clock\(\).uninstall\(\)/g, 'jest.useRealTimers()');
    result = result.replace(/jasmine.clock\(\).mockDate\((.*)\)/g, 'advanceTo($1)');


    // if (!result.includes('@ngneat/spectator') && result.includes('SpyObject')) {
    //   result = 'import { SpyObject } from \'@ngneat/spectator/jest\';\r\n' + result;
    // }
    // if (result.includes('MatDialog') && !result.includes('@angular/material/dialog')) {
    //   result = result.replace(/import \{(.*)MatDialog, (.*)\}/g, 'import {$1$2}');
    //   result = result.replace(/import \{(.*)MatDialogModule, (.*)\}/g, 'import {$1$2}');
    //   result = result.replace(/import \{(.*)MatDialogModule(.*)\}/g, 'import {$1$2}');
    //   result = result.replace(/import \{(.*)MAT_DIALOG_DATA, (.*)\}/g, 'import {$1$2}');
    //   result = result.replace(/import \{(.*)MatDialogRef, (.*)\}/g, 'import {$1$2}');
    //   result = 'import { MatDialog, MatDialogModule, MAT_DIALOG_DATA, MatDialogRef } from \'@angular/material/dialog\';\r\n' + result;
    // }

    // if (result.includes('withArgs')) {
    //   result = result.replace(/(.*)\.withArgs\((.*)\)\.mockReturnValue\((.*)\)/g, `$1.mockImplementation(flag => {
    //     switch (flag) {
    //       case $2:
    //         return $3;
    //     }
    //   })`);
    // }

    result = result.replace(/jest\.jest/g, 'jest');

    let newFile = filename.replace('.spec.ts', '.test.ts');
    fs.writeFile(newFile, result, 'utf8', function (err) {
      if (err)
        return console.log(err);
      console.log('Successfully wrote ' + newFile);
      if (newFile != filename) {
        fs.unlinkSync(filename);
      }
    });
  });
}

createSpy.ts

export const createSpyObj = <T = any>(_baseName, methodNames?): jest.Mocked<T> => {
  const obj: any = {};

  for (let i = 0; i < methodNames.length; i++) {
    obj[methodNames[i]] = jest.fn();
  }

  return obj;
};

export const createSpy = (_baseName?) => {
  return jest.fn();
};
  

jest-bullet.ts

// This code has been adapted from ng-bullet and modified to work with Jest
// https://www.npmjs.com/package/ng-bullet

import { Type } from '@angular/core';
import { ComponentFixture, getTestBed, TestBed } from '@angular/core/testing';

/**
 * Reconfigures current test suit to prevent angular components re-compilation after every test run.
 * Forces angular test bed to re-create zone and all injectable services by directly
 * setting _instantiated variable to false after every test run.
 * Cleanups all the changes and reverts test bed configuration after suite has finished.
 *
 * @param configureAction an optional delegate which can be used to configure test bed for the current test suite
 * directly in the configureTestSuite call (you don't need extra BeforeAll in this case)
 */
export const configureTestSuite = (configureAction?: () => void) => {
    const testBedApi: any = getTestBed();
    const originReset = TestBed.resetTestingModule;

    beforeAll(() => {
        TestBed.resetTestingModule();
        TestBed.resetTestingModule = () => TestBed;
    });

    if (configureAction) {
        beforeAll((done?: jest.DoneCallback) => (async () => {
            configureAction();
            await TestBed.compileComponents();
        })().then(done ? done : () => {}).catch(done && done.fail ? done.fail : err => console.log(err)));
    }

    afterEach(() => {
        testBedApi._activeFixtures.forEach((fixture: ComponentFixture<any>) => fixture.destroy());
        testBedApi._instantiated = false;
    });

    afterAll(() => {
        TestBed.resetTestingModule = originReset;
        TestBed.resetTestingModule();
    });
};

/**
 * A wrapper class around ComponentFixture, which provides useful accessros:
 * component - to access component instance of current the fixture
 * element - to access underlying native element of the current component
 * detectChanges - to run change detections using current fixture
 * resolve - to resolve a type using current fixture's injector
 */
export class TestCtx<T> {
    constructor(public fixture: ComponentFixture<T>) { }

    public get component() { return this.fixture.componentInstance; }

    public get element(): HTMLElement { return this.fixture.debugElement.nativeElement; }

    public detectChanges() { this.fixture.detectChanges(); }

    public resolve(component: Type<any>) { return this.fixture.debugElement.injector.get(component); }
}

/**
 * Creates TestCtx instance for the Angular Component which is not initialized yet (no ngOnInit called)
 * Use case: you can override Component's providers before hooks are called.
 *
 * @param component - type of component to create instance of
 * **/
export const createTestContext = <T>(component: Type<T>) => {
    const fixture = TestBed.createComponent<T>(component);
    const testCtx = new TestCtx<T>(fixture);
    return testCtx;
};

/**Same as @function createTestContext, but waits till fixture becomes stable */
export const createStableTestContext = async <T>(component: Type<T>) => {
    const testCtx = createTestContext(component);
    testCtx.detectChanges();
    await testCtx.fixture.whenStable();
    testCtx.detectChanges();
    return testCtx;
};

jest.config.js

var preset = require("jest-preset-angular/jest-preset");
module.exports = {
  ...preset,
  preset: "jest-preset-angular",
  setupFiles: ["jest-date-mock"],
  setupFilesAfterEnv: [
    "<rootDir>/node_modules/jest-preset-angular/build/setupJest.js"
  ],
  testMatch: ["**/*.test.ts"],
  globals: {
    ...preset.globals,
    "ts-jest": {
      ...preset.globals["ts-jest"],
      tsConfig: "tsconfig.test.json",
      isolatedModules: true
    }
  },
  transform: {
    "^.+\\.(j|t)sx?$": "ts-jest",
  },
  transformIgnorePatterns: [
    "<rootDir>/node_modules/(?!lodash-es/.*)"
  ],
  coverageReporters: ['html', 'lcovonly', 'text-summary'],
  coverageDirectory: '<rootDir>/coverage'
};

setupJest.ts

import 'jest-preset-angular';

tsconfig.test.json

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "mapRoot": "./",
    "outDir": "./out-tsc/spec",
    "types": [
      "@jest/types",
      "node"
    ],
    "esModuleInterop": true,
    "allowJs": true
  }
}