🧪 Add e2e tests with Cypress

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

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+/// <reference types="cypress" />
+// remove no check once Cypress.sinon is typed
+// https://github.com/cypress-io/cypress/issues/6720
+
+context('Spies, Stubs, and Clock', () => {
+  it('cy.spy() - wrap a method in a spy', () => {
+    // https://on.cypress.io/spy
+    cy.visit('https://example.cypress.io/commands/spies-stubs-clocks')
+
+    const obj = {
+      foo () {},
+    }
+
+    const spy = cy.spy(obj, 'foo').as('anyArgs')
+
+    obj.foo()
+
+    expect(spy).to.be.called
+  })
+
+  it('cy.spy() retries until assertions pass', () => {
+    cy.visit('https://example.cypress.io/commands/spies-stubs-clocks')
+
+    const obj = {
+      /**
+       * Prints the argument passed
+       * @param x {any}
+      */
+      foo (x) {
+        console.log('obj.foo called with', x)
+      },
+    }
+
+    cy.spy(obj, 'foo').as('foo')
+
+    setTimeout(() => {
+      obj.foo('first')
+    }, 500)
+
+    setTimeout(() => {
+      obj.foo('second')
+    }, 2500)
+
+    cy.get('@foo').should('have.been.calledTwice')
+  })
+
+  it('cy.stub() - create a stub and/or replace a function with stub', () => {
+    // https://on.cypress.io/stub
+    cy.visit('https://example.cypress.io/commands/spies-stubs-clocks')
+
+    const obj = {
+      /**
+       * prints both arguments to the console
+       * @param a {string}
+       * @param b {string}
+      */
+      foo (a, b) {
+        console.log('a', a, 'b', b)
+      },
+    }
+
+    const stub = cy.stub(obj, 'foo').as('foo')
+
+    obj.foo('foo', 'bar')
+
+    expect(stub).to.be.called
+  })
+
+  it('cy.clock() - control time in the browser', () => {
+    // https://on.cypress.io/clock
+
+    // create the date in UTC so its always the same
+    // no matter what local timezone the browser is running in
+    const now = new Date(Date.UTC(2017, 2, 14)).getTime()
+
+    cy.clock(now)
+    cy.visit('https://example.cypress.io/commands/spies-stubs-clocks')
+    cy.get('#clock-div').click()
+      .should('have.text', '1489449600')
+  })
+
+  it('cy.tick() - move time in the browser', () => {
+    // https://on.cypress.io/tick
+
+    // create the date in UTC so its always the same
+    // no matter what local timezone the browser is running in
+    const now = new Date(Date.UTC(2017, 2, 14)).getTime()
+
+    cy.clock(now)
+    cy.visit('https://example.cypress.io/commands/spies-stubs-clocks')
+    cy.get('#tick-div').click()
+      .should('have.text', '1489449600')
+
+    cy.tick(10000) // 10 seconds passed
+    cy.get('#tick-div').click()
+      .should('have.text', '1489449610')
+  })
+
+  it('cy.stub() matches depending on arguments', () => {
+    // see all possible matchers at
+    // https://sinonjs.org/releases/latest/matchers/
+    const greeter = {
+      /**
+       * Greets a person
+       * @param {string} name
+      */
+      greet (name) {
+        return `Hello, ${name}!`
+      },
+    }
+
+    cy.stub(greeter, 'greet')
+      .callThrough() // if you want non-matched calls to call the real method
+      .withArgs(Cypress.sinon.match.string).returns('Hi')
+      .withArgs(Cypress.sinon.match.number).throws(new Error('Invalid name'))
+
+    expect(greeter.greet('World')).to.equal('Hi')
+    // @ts-ignore
+    expect(() => greeter.greet(42)).to.throw('Invalid name')
+    expect(greeter.greet).to.have.been.calledTwice
+
+    // non-matched calls goes the actual method
+    // @ts-ignore
+    expect(greeter.greet()).to.equal('Hello, undefined!')
+  })
+
+  it('matches call arguments using Sinon matchers', () => {
+    // see all possible matchers at
+    // https://sinonjs.org/releases/latest/matchers/
+    const calculator = {
+      /**
+       * returns the sum of two arguments
+       * @param a {number}
+       * @param b {number}
+      */
+      add (a, b) {
+        return a + b
+      },
+    }
+
+    const spy = cy.spy(calculator, 'add').as('add')
+
+    expect(calculator.add(2, 3)).to.equal(5)
+
+    // if we want to assert the exact values used during the call
+    expect(spy).to.be.calledWith(2, 3)
+
+    // let's confirm "add" method was called with two numbers
+    expect(spy).to.be.calledWith(Cypress.sinon.match.number, Cypress.sinon.match.number)
+
+    // alternatively, provide the value to match
+    expect(spy).to.be.calledWith(Cypress.sinon.match(2), Cypress.sinon.match(3))
+
+    // match any value
+    expect(spy).to.be.calledWith(Cypress.sinon.match.any, 3)
+
+    // match any value from a list
+    expect(spy).to.be.calledWith(Cypress.sinon.match.in([1, 2, 3]), 3)
+
+    /**
+     * Returns true if the given number is event
+     * @param {number} x
+     */
+    const isEven = (x) => x % 2 === 0
+
+    // expect the value to pass a custom predicate function
+    // the second argument to "sinon.match(predicate, message)" is
+    // shown if the predicate does not pass and assertion fails
+    expect(spy).to.be.calledWith(Cypress.sinon.match(isEven, 'isEven'), 3)
+
+    /**
+     * Returns a function that checks if a given number is larger than the limit
+     * @param {number} limit
+     * @returns {(x: number) => boolean}
+     */
+    const isGreaterThan = (limit) => (x) => x > limit
+
+    /**
+     * Returns a function that checks if a given number is less than the limit
+     * @param {number} limit
+     * @returns {(x: number) => boolean}
+     */
+    const isLessThan = (limit) => (x) => x < limit
+
+    // you can combine several matchers using "and", "or"
+    expect(spy).to.be.calledWith(
+      Cypress.sinon.match.number,
+      Cypress.sinon.match(isGreaterThan(2), '> 2').and(Cypress.sinon.match(isLessThan(4), '< 4')),
+    )
+
+    expect(spy).to.be.calledWith(
+      Cypress.sinon.match.number,
+      Cypress.sinon.match(isGreaterThan(200), '> 200').or(Cypress.sinon.match(3)),
+    )
+
+    // matchers can be used from BDD assertions
+    cy.get('@add').should('have.been.calledWith',
+      Cypress.sinon.match.number, Cypress.sinon.match(3))
+
+    // you can alias matchers for shorter test code
+    const { match: M } = Cypress.sinon
+
+    cy.get('@add').should('have.been.calledWith', M.number, M(3))
+  })
+})