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Unit-Testing in Angular mit Jest

Unit-Testing in Angular mit Jest

Unit-Tests sind ein hervorragendes Mittel, um (kritische) Funktionalität einer Anwendung automatisiert und schnell überprüfen zu lassen. Das SPA-Framework Angular liefert mit Karma von vornherein eine Testunterstützung mit. Mit Facebooks Jest gibt es jedoch ein weiteres Framework, das unter anderem mit paralleler Testausführung lockt.

In diesem Webinar zeigt Ihnen Christian Liebel, wie Sie Ihre Angular-App mithilfe von Jest testen können. Nachdem wir zu Beginn ein gemeinsames Verständnis zum Thema Unit Tests geschaffen haben, werden wir uns abschließend auch fortgeschrittenen Inhalten wie Spys und Mocks nähern.

Christian Liebel

February 03, 2021
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  1. 1. Testing Overview 2. Unit Testing Basics 3. Jest vs.

    Karma/Jasmine 4. Testing with Jest 5. Spies & Mocks 6. E2E Tests Overview Angular Unit Testing Agenda
  2. Test Types End-to-end Tests (~ 1000 ms, 10%) Acceptance tests

    simulating a real user Integration Tests (~ 100 ms, 20%) Tests the integration of different modules Unit Tests (~ 10 ms, 70 %) Tests a class, method or algorithm Angular Unit Testing Testing Overview
  3. Test-Driven Development First, write your test (= requirements!) See it

    failing Next, write the minimum required implementation to fulfill the test See your test turn green (Refactor) Repeat Angular Unit Testing Unit Testing Basics
  4. Brownfield Testing Use Extract Method refactoring to… - reduce complexity

    of large methods (target method length: 7±2 lines) - avoid more than one nesting/indent level Move large blocks of code in own files or services (target file length: ±100 lines) Angular Unit Testing Unit Testing Basics
  5. A-TRIP Pattern Unit Tests should be… - Automatic (no user

    interaction required) - Thorough (test critical functionality) - Repeatable (repeated execution leads to same result) - Independent (order does not matter) - Professional (test code doesn’t test itself) Angular Unit Testing Unit Testing Basics
  6. Unit Testing Support Unit Tests (~ 10 ms, 70 %)

    Tests a class, method or algorithm Integration Tests (~ 100 ms, 20%) Tests the integration of different modules End-to-end Tests (~ 1000 ms, 10%) Acceptance tests simulating a real user Angular Unit Testing Angular
  7. Unit Testing Support Angular CLI schematics automatically create a test

    specification file (*.spec.ts) for each generated unit. Angular Unit Testing Angular
  8. Angular’s Default Testing System - Does not require additional project

    configuration - Requires a browser (e.g. Chrome Headless for CI environments) - Tests run sequentially Angular Unit Testing Karma & Jasmine
  9. Test runner Angular Unit Testing Jest - Fast: Tests run

    in parallel - Easy CI setup: No browser required (JSDom) - Setup: ng add @briebug/jest-schematic - Jasmine BDD testing framework is mostly compatible with Jest - Migration: npx jest-codemods
  10. Simple Test describe("A suite is just a function", () =>

    { let a; test("and so is a spec", () => { a = true; expect(a).toBe(true); }); }); Angular Unit Testing Jest
  11. AAA Pattern Arrange const x = …; Act const result

    = sut.myTestMethod(x); Assert expect(result).toBeDefined(); Angular Unit Testing Unit Tests
  12. Matchers expect(123).toBe(123); expect({ foo: 123 }).toEqual({ foo: 123 }); expect([1,

    2, 3]).toContain(3); expect(false).toBeFalsy(); expect(1).toBeTruthy(); expect(null).toBeNull(); expect(undefined).toBeUndefined(); expect(999).toBeDefined(); expect(() => method()).toThrow(); Angular Unit Testing Jest
  13. Suggestion describe('FooService', () => { describe('method', () => { test('should

    do this', () => {}); test('should do that', () => {}); }); }); - 1 suite per class - 1 suite per method - n tests (use “should” and prevent “and”) Angular Unit Testing Jest
  14. Setup/Teardown Run before/after each test in this suite beforeEach afterEach

    Run before/after all tests in this suite beforeAll afterAll Angular Unit Testing Jest
  15. Excluding/including tests Exclude this test (suite) describe.skip test.skip Only include

    this test (suite) describe.only test.only Angular Unit Testing Jest
  16. Unit Testing Commands Unit Tests (Karma/Jest) npm test ng test

    ng t End-to-end Tests (Protractor) ng e2e ng e Angular Unit Testing Angular
  17. Repetitive tests test.each` a | b | expected ${1} |

    ${1} | ${2} ${1} | ${2} | ${3} ${2} | ${1} | ${3} `('returns $expected when $a is added $b', ({a, b, expected}) => { expect(a + b).toBe(expected); }); Angular Unit Testing Jest https://jestjs.io/docs/en/api#testeachtablename-fn-timeout
  18. Mock Functions const mock = jest.fn(x => 42 + x);

    // The mock function is called twice expect(mockCallback.mock.calls.length).toBe(2); // The first argument of the second call to the function was 1 expect(mockCallback.mock.calls[1][0]).toBe(1); Angular Unit Testing Jest https://jestjs.io/docs/en/mock-functions
  19. Spies jest.spyOn(existingObject, 'existingFunction'); // spyOn also calls the function, alternatives:

    // jest.spyOn(/* … */).mockImplementation(() => 42); // existingObject['existingFunction'] = jest.fn(() => 42); expect(existingObject.existingFunction).toHaveBeenCalled(); // optional: toHaveBeenCalledWith(arg1, arg2) // optional: toHaveBeenCalledTimes(4) Angular Unit Testing Jest
  20. Basics // Creating mock let mockedFoo:Foo = mock(Foo); // Getting

    instance from mock let foo:Foo = instance(mockedFoo); // Using instance in source code foo.getBar(5); // Explicit, readable verification verify(mockedFoo.getBar(5)).called(); Angular Unit Testing ts-mockito https://www.npmjs.com/package/ts-mockito
  21. Stubbing Method Calls // Creating mock let mockedFoo:Foo = mock(Foo);

    // stub method before execution when(mockedFoo.getBar(3)).thenReturn('three'); // Getting instance let foo:Foo = instance(mockedFoo); // prints three console.log(foo.getBar(3)); Angular Unit Testing ts-mockito https://www.npmjs.com/package/ts-mockito
  22. AAA Pattern & Mocks Arrange const x = …; Setup

    when(mock.myOtherMethod).thenReturn(3); Act const result = sut.myTestMethod(x); Assert expect(result).toBeDefined(); Verify verify(mock.myOtherMethod).called(); Angular Unit Testing Unit Tests
  23. Testing Utilities: TestBed describe('Component: Login', () => { beforeEach(() =>

    { TestBed.configureTestingModule({ declarations: [LoginComponent], providers: [AuthService] }); }); }); Angular Unit Testing Angular https://codecraft.tv/courses/angular/unit-testing/angular-test-bed/
  24. Snapshot Testing test('should create the app', () => { const

    fixture = TestBed.createComponent(AppComponent); expect(fixture).toMatchSnapshot(); }); Angular Unit Testing Jest <h1>Hallo</h1> <h1>Hxllo</h1>
  25. Test Harnesses test('should mark confirmed when ok button clicked', async

    () => { const okButton = await loader.getHarness(MatButtonHarness.with({selector: '.confirm'}); expect(fixture.componentInstance.confirmed).toBe(false); expect(await okButton.isDisabled()).toBe(false); await okButton.click(); expect(fixture.componentInstance.confirmed).toBe(true); }); https://material.angular.io/guide/using-component-harnesses Angular Unit Testing Angular
  26. Testing Utilities: fakeAsync describe('this test', () => { test('looks async

    but is synchronous', fakeAsync((): void => { let flag = false; setTimeout(() => { flag = true; }, 100); expect(flag).toBe(false); tick(50); expect(flag).toBe(false); tick(50); expect(flag).toBe(true); })); }); Angular Unit Testing Angular https://angular.io/api/core/testing/fakeAsync
  27. Code Coverage npm test -- --coverage Code coverage provided by

    Istanbul Coverage metadata written to coverage folder Code coverage policy: ~ 80% Angular Unit Testing Angular