Cypress Harness

The Background Story

Both unit-testing and e2e testing can get tricky when it comes to interacting with the DOM. In fact, tests have to be decoupled from the implementation details of the code they test. Especially if you are interacting with same components of an app in different tests.

This often happens with UI libraries like Angular Material and that is why the Angular Material's team came up with the amazing idea of creating a testing abstraction layer over components called Component Test Harnesses.

One of the most interesting ideas behind Component Test Harnesses is that they are also meant to be platform agnostic, which means they can be used in your unit-tests with Jest or Karma, in your e2e tests with Protractor or Cypress or in your Cypress Component Tests.

This library provides Cypress support to Component Test Harnesses.

!Angular Material Datepicker Harness in Cypress

Setup

$3

``shell
yarn add -D @jscutlery/cypress-harness @angular/cdk cypress-pipe

or

npm install -D @jscutlery/cypress-harness @angular/cdk cypress-pipe
`

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#### 2.a. Cypress E2E

Update your e2e folder's cypress/support/e2e.ts and add:

`ts
import '@jscutlery/cypress-harness/support';
`

then update the cypress.config.ts file as follows:

`ts
import { defineConfig } from 'cypress';
import { getPreprocessorConfig } from '@jscutlery/cypress-harness/preprocessor-config';

export default defineConfig({
e2e: {
// ... other existing settings if any (like nxE2EPreset() if using Nx).
...getPreprocessorConfig(),
},
});
`

This last part is needed to add support for package exports conditionals
and allow us to import harnesses from @angular/cdk/testing for example.

#### 2.b. Cypress Component Testing

If you are using Cypress Component Testing then there is a different import to add to the following file: cypress/support/component.ts:

`ts
import '@jscutlery/cypress-harness/support-ct';
`

_(the getPreprocessorConfig() is not required here as it is already set up by cypress/angular.)_

Usage

`ts
describe('datepicker', () => {
/* getHarness & getAllHarnesses are lazy so you can
initialize them wherever you want and reuse them. /
const datepicker = getHarness(MatDatepickerInputHarness);
const calendars = getAllHarnesses(MatCalendarHarness);

it('should set date', () => {
cy.visit('/'); // or cy.mount(MyComponent); for component testing.
datepicker.setValue('1/1/2010');
datepicker.openCalendar();
datepicker.getCalendar().then((harness) => harness.next()); // next method is already used
datepicker.getCalendar().selectCell({ text: '10' });
datepicker.getValue().should('equal', '2/10/2010');
calendars.should('be.empty');
});
});
``