Angular Unit Testing 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 dieser Session 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.

Transcript

1. Angular Unit Testing mit Jest Christian Liebel @christianliebel Consultant
2. The image part with relationship ID rId12 was not found in the file. The image part with relationship ID rId12 was not found in the file. Special Day Modern Business Applications Thema Sprecher Datum, Uhrzeit Web-API mit Turbo: Deep-dive in async/await bei Backend-APIs Sebastian Gingter DI, 21. September 2021, 10.45 bis 11.45 Web Components in modernen Web-Apps: Hype oder Heilsbringer? Peter Kröner DI, 21. September 2021, 12.15 bis 13.15 Produktivitäts-PWAs mit Angular auf Desktopniveau Christian Liebel DI, 21. September 2021, 14.30 bis 15.30 Angular Unit Testing mit Jest Christian Liebel DI, 21. September 2021, 16.00 bis 17.00 SPAs in Azure betreiben - ein Leitfaden aus der Praxis Thorsten Hans MI, 22. September 2021, 17.30 bis 18.30
3. 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 mit Jest Agenda
4. 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 mit Jest Testing Overview
5. 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 mit Jest Unit Testing Basics
6. 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 mit Jest Unit Testing Basics
7. 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 mit Jest Unit Testing Basics
8. 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 mit Jest Angular
9. Unit Testing Support Angular CLI schematics automatically create a test specification file (*.spec.ts) for each generated unit. Angular Unit Testing mit Jest Angular
10. 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 mit Jest Karma & Jasmine
11. Test runner Angular Unit Testing mit Jest 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
12. Introduction https://jestjs.io/docs/en/getting-started Angular Unit Testing mit Jest Jest
13. 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 mit Jest Jest
14. AAA Pattern Arrange const x = …; Act const result = sut.myTestMethod(x); Assert expect(result).toBeDefined(); Angular Unit Testing mit Jest Unit Tests
15. 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 mit Jest Jest
16. 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 mit Jest Jest
17. 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 mit Jest Jest
18. Excluding/including tests Exclude this test (suite) describe.skip test.skip Only include this test (suite) describe.only test.only Angular Unit Testing mit Jest Jest
19. Test Reminders Remind me to write a test test.todo Angular Unit Testing mit Jest Jest
20. Unit Testing Commands Unit Tests (Karma/Jest) npm test ng test ng t End-to-end Tests ng e2e ng e Angular Unit Testing mit Jest Angular
21. Angular Unit Testing mit Jest DEMO: Testing Angular Pipes
22. 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 mit Jest Jest https://jestjs.io/docs/en/api#testeachtablename-fn-timeout
23. 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 mit Jest Jest https://jestjs.io/docs/en/mock-functions
24. 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 mit Jest Jest
25. 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 mit Jest ts-mockito https://www.npmjs.com/package/ts-mockito
26. 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 mit Jest ts-mockito https://www.npmjs.com/package/ts-mockito
27. 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 mit Jest Unit Tests
28. Angular Unit Testing mit Jest DEMO: Mocking Dependencies
29. Testing Utilities: TestBed describe('Component: Login', () => { beforeEach(() => { TestBed.configureTestingModule({ declarations: [LoginComponent], providers: [AuthService] }); }); }); Angular Unit Testing mit Jest Angular https://codecraft.tv/courses/angular/unit-testing/angular-test-bed/
30. Angular Unit Testing mit Jest DEMO: Using the TestBed
31. Snapshot Testing test('should create the app', () => { const fixture = TestBed.createComponent(AppComponent); expect(fixture).toMatchSnapshot(); }); Angular Unit Testing mit Jest Jest <h1>Hallo</h1> <h1>Hxllo</h1>
32. Angular Unit Testing mit Jest DEMO: Snapshot Testing
33. Test Watcher npm test -- --watch npm test -- --watch-all Angular Unit Testing mit Jest Jest
34. Code Coverage npm test -- --coverage Code coverage provided by Istanbul Coverage metadata written to coverage folder Code coverage policy: ~ 80% Angular Unit Testing mit Jest Angular
35. Cypress https://www.cypress.io/ DevExpress TestCafé https://devexpress.github.io/testcafe/ Angular Unit Testing mit Jest E2E Tests
36. Thank you for your kind attention! Christian Liebel @christianliebel christian.liebel@thinktecture.com