🧪 Add e2e tests with Cypress

frontend/cypress/integration-examples/2-advanced-examples/assertions.spec.js

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+/// <reference types="cypress" />
+
+context('Assertions', () => {
+  beforeEach(() => {
+    cy.visit('https://example.cypress.io/commands/assertions')
+  })
+
+  describe('Implicit Assertions', () => {
+    it('.should() - make an assertion about the current subject', () => {
+      // https://on.cypress.io/should
+      cy.get('.assertion-table')
+        .find('tbody tr:last')
+        .should('have.class', 'success')
+        .find('td')
+        .first()
+        // checking the text of the <td> element in various ways
+        .should('have.text', 'Column content')
+        .should('contain', 'Column content')
+        .should('have.html', 'Column content')
+        // chai-jquery uses "is()" to check if element matches selector
+        .should('match', 'td')
+        // to match text content against a regular expression
+        // first need to invoke jQuery method text()
+        // and then match using regular expression
+        .invoke('text')
+        .should('match', /column content/i)
+
+      // a better way to check element's text content against a regular expression
+      // is to use "cy.contains"
+      // https://on.cypress.io/contains
+      cy.get('.assertion-table')
+        .find('tbody tr:last')
+        // finds first <td> element with text content matching regular expression
+        .contains('td', /column content/i)
+        .should('be.visible')
+
+      // for more information about asserting element's text
+      // see https://on.cypress.io/using-cypress-faq#How-do-I-get-an-element’s-text-contents
+    })
+
+    it('.and() - chain multiple assertions together', () => {
+      // https://on.cypress.io/and
+      cy.get('.assertions-link')
+        .should('have.class', 'active')
+        .and('have.attr', 'href')
+        .and('include', 'cypress.io')
+    })
+  })
+
+  describe('Explicit Assertions', () => {
+    // https://on.cypress.io/assertions
+    it('expect - make an assertion about a specified subject', () => {
+      // We can use Chai's BDD style assertions
+      expect(true).to.be.true
+      const o = { foo: 'bar' }
+
+      expect(o).to.equal(o)
+      expect(o).to.deep.equal({ foo: 'bar' })
+      // matching text using regular expression
+      expect('FooBar').to.match(/bar$/i)
+    })
+
+    it('pass your own callback function to should()', () => {
+      // Pass a function to should that can have any number
+      // of explicit assertions within it.
+      // The ".should(cb)" function will be retried
+      // automatically until it passes all your explicit assertions or times out.
+      cy.get('.assertions-p')
+        .find('p')
+        .should(($p) => {
+          // https://on.cypress.io/$
+          // return an array of texts from all of the p's
+          // @ts-ignore TS6133 unused variable
+          const texts = $p.map((i, el) => Cypress.$(el).text())
+
+          // jquery map returns jquery object
+          // and .get() convert this to simple array
+          const paragraphs = texts.get()
+
+          // array should have length of 3
+          expect(paragraphs, 'has 3 paragraphs').to.have.length(3)
+
+          // use second argument to expect(...) to provide clear
+          // message with each assertion
+          expect(paragraphs, 'has expected text in each paragraph').to.deep.eq([
+            'Some text from first p',
+            'More text from second p',
+            'And even more text from third p',
+          ])
+        })
+    })
+
+    it('finds element by class name regex', () => {
+      cy.get('.docs-header')
+        .find('div')
+        // .should(cb) callback function will be retried
+        .should(($div) => {
+          expect($div).to.have.length(1)
+
+          const className = $div[0].className
+
+          expect(className).to.match(/heading-/)
+        })
+        // .then(cb) callback is not retried,
+        // it either passes or fails
+        .then(($div) => {
+          expect($div, 'text content').to.have.text('Introduction')
+        })
+    })
+
+    it('can throw any error', () => {
+      cy.get('.docs-header')
+        .find('div')
+        .should(($div) => {
+          if ($div.length !== 1) {
+            // you can throw your own errors
+            throw new Error('Did not find 1 element')
+          }
+
+          const className = $div[0].className
+
+          if (!className.match(/heading-/)) {
+            throw new Error(`Could not find class "heading-" in ${className}`)
+          }
+        })
+    })
+
+    it('matches unknown text between two elements', () => {
+      /**
+       * Text from the first element.
+       * @type {string}
+      */
+      let text
+
+      /**
+       * Normalizes passed text,
+       * useful before comparing text with spaces and different capitalization.
+       * @param {string} s Text to normalize
+      */
+      const normalizeText = (s) => s.replace(/\s/g, '').toLowerCase()
+
+      cy.get('.two-elements')
+        .find('.first')
+        .then(($first) => {
+          // save text from the first element
+          text = normalizeText($first.text())
+        })
+
+      cy.get('.two-elements')
+        .find('.second')
+        .should(($div) => {
+          // we can massage text before comparing
+          const secondText = normalizeText($div.text())
+
+          expect(secondText, 'second text').to.equal(text)
+        })
+    })
+
+    it('assert - assert shape of an object', () => {
+      const person = {
+        name: 'Joe',
+        age: 20,
+      }
+
+      assert.isObject(person, 'value is object')
+    })
+
+    it('retries the should callback until assertions pass', () => {
+      cy.get('#random-number')
+        .should(($div) => {
+          const n = parseFloat($div.text())
+
+          expect(n).to.be.gte(1).and.be.lte(10)
+        })
+    })
+  })
+})