How to test APIs with Cypress

On today's “Pinches of Cypress”, learn how to test APIs with Cypress.io?

To illustrate, I will use ServeRest, a project created by Paulo Gonçalves to help with API testing studies.

This post will focus only on GET requests, ok?

Some of ServeRest's features are the search for users, products, and carts.

Let's start with a search for users test.

describe('GET users', () => {
  it('correctly gets users', () => {
    cy.request({
      method: 'GET',
      url: 'http://localhost:3000/usuarios'
    }).then((response) => {
      expect(response.status).to.equal(200);
      expect(response.body.usuarios[0].nome).to.equal('Fulano da Silva')
      expect(response.body.usuarios[0].email).to.equal('fulano@qa.com')
    })
  })
})

Note: the endpoints and body responses from ServeRest are in Portuguese. Sorry about that!

As you can see in the above code snippet, in addition to checking that the status of the response is successful (200), I also perform checks on the structure of the response body to ensure that the name (nome in PT-BR) and email of the first user returned is as expected.

Now, let's look at a search for products test, where I want to check more than one product, not just the first.

describe('GET products', () => {
  it('correctly gets products', () => {
    const expectedResult = [
      {
        name: 'Logitech MX Vertical',
        description: 'Mouse',
        price: 470,
        quantity: 382
      },
      {
        name: 'Samsung 60 polegadas',
        description: 'TV',
        price: 5240,
        quantity: 49977
      }
    ]

    cy.request({
      method: 'GET',
      url: 'http://localhost:3000/produtos'
    }).then((response) => {
      expect(response.status).to.equal(200);
      response.body.produtos.forEach((product, index) => {
        expect(product.nome).to.equal(expectedResult[index].name)
        expect(product.descricao).to.equal(expectedResult[index].description)
        expect(product.preco).to.equal(expectedResult[index].price)
        expect(product.quantidade).to.equal(expectedResult[index].quantity)
      })
    })
  })
})

In the above example, I define an array with the expected result (which could even come from a fixture, but I will talk about this in another post).

The array contains two objects, both with the name, description, price, and quantity properties (nome, descricao, preco and quantidade in PT-BR).

Finally, I make a GET request to the /products endpoint, and with the return of the request, I check the success status of the response, in addition to iterating through all the products returned in the response body (using the JavaScript forEach functionality) to verify that the name, description, price and quantity are as per the expected result.

As the last example, let's see a test where I search for carts, passing as a specific total quantity as queryString.

describe('GET carts', () => {
  it('correctly gets carts by total quantity', () => {
    cy.request({
      method: 'GET',
      url: 'http://localhost:3000/carrinhos?quantidadeTotal=3'
    }).then((response) => {
      expect(response.status).to.equal(200);
      expect(response.body.carrinhos.length).to.equal(1)
    })
  })
})

In the above test, I verify that only one cart was returned in the cart's array from the body of the response (using the length property), in addition to the success status, of course. 😉

Running the three tests above locally, they all passed, and in just 146ms. 🚀

I keep collecting feedback and creating a backlog for the next posts. Leave a comment with what you would like me to address in future content.

This post was originally published in Portuguese on the Talking About Testing blog.

Would you like to learn about test automation with Cypress? Get to know my online courses on Udemy.

Spoiler: in 2021, there will be an API testing with Cypress course at the Talking About Testing school. Stay tuned!