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Working with GraphQL

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What you'll learn​

  • Best practices to alias multiple GraphQL queries or mutations for a group of tests.
  • Overriding an existing intercept to modify the query or mutation response
  • Asserting against a GraphQL query or mutation response

The strategies below follow best known practices for waiting and asserting against GraphQL queries or mutations.

Waiting and asserting on GraphQL API requests rely on matching a query or mutation name in the POST body.

Using cy.intercept() we can override the response to a GraphQL query or mutation by declaring an intercept at the beginning of the test or closer to the expectation.

Alias multiple queries or mutations​

In the beforeEach, we will use cy.intercept() to capture all requests for a GraphQL endpoint (e.g. /graphql), use conditionals to match the query or mutation and set an alias for using req.alias.

First, we'll create a set of utility functions to help match and alias our queries and mutations.

// utils/graphql-test-utils.js

// Utility to match GraphQL mutation based on the operation name
export const hasOperationName = (req, operationName) => {
  const { body } = req
  return (
    Object.prototype.hasOwnProperty.call(body, 'operationName') &&
    body.operationName === operationName
  )
}

// Alias query if operationName matches
export const aliasQuery = (req, operationName) => {
  if (hasOperationName(req, operationName)) {
    req.alias = `gql${operationName}Query`
  }
}

// Alias mutation if operationName matches
export const aliasMutation = (req, operationName) => {
  if (hasOperationName(req, operationName)) {
    req.alias = `gql${operationName}Mutation`
  }
}

In our test file, we can import these utilities and use them to alias the queries and mutations for our tests in a beforeEach.

// app.cy.js
import { aliasQuery, aliasMutation } from '../utils/graphql-test-utils'

context('Tests', () => {
  beforeEach(() => {
    cy.intercept('POST', 'http://localhost:3000/graphql', (req) => {
      // Queries
      aliasQuery(req, 'GetLaunchList')
      aliasQuery(req, 'LaunchDetails')
      aliasQuery(req, 'GetMyTrips')

      // Mutations
      aliasMutation(req, 'Login')
      aliasMutation(req, 'BookTrips')
    })
  })
  // ...
})

Expectations for Query or Mutation Results​

Expectations can be made against the response of an intercepted GraphQL query or mutation using cy.wait().

// app.cy.js
import { aliasQuery } from '../utils/graphql-test-utils'

context('Tests', () => {
  beforeEach(() => {
    cy.intercept('POST', 'http://localhost:3000/graphql', (req) => {
      // Queries
      aliasQuery(req, 'Login')

      // ...
    })
  })

  it('should verify login data', () => {
    cy.wait('@gqlLoginQuery')
      .its('response.body.data.login')
      .should('have.property', 'id')
      .and('have.property', 'token')
  })
})

Modifying a Query or Mutation Response​

In the test below, the response is modified to test the UI for a single page of results.

// app.cy.js
import { hasOperationName, aliasQuery } from '../utils/graphql-test-utils'

context('Tests', () => {
  beforeEach(() => {
    cy.intercept('POST', 'http://localhost:3000/graphql', (req) => {
      // Queries
      aliasQuery(req, 'GetLaunchList')

      // ...
    })
  })

  it('should not display the load more button on the launches page', () => {
    cy.intercept('POST', 'http://localhost:3000/graphql', (req) => {
      const { body } = req
      if (hasOperationName(req, 'GetLaunchList')) {
        // Declare the alias from the initial intercept in the beforeEach
        req.alias = 'gqlGetLaunchListQuery'

        // Set req.fixture or use req.reply to modify portions of the response
        req.reply((res) => {
          // Modify the response body directly
          res.body.data.launches.hasMore = false
          res.body.data.launches.launches =
            res.body.data.launches.launches.slice(5)
        })
      }
    })

    // Must visit after cy.intercept
    cy.visit('/')

    cy.wait('@gqlGetLaunchListQuery')
      .its('response.body.data.launches')
      .should((launches) => {
        expect(launches.hasMore).to.be.false
        expect(launches.length).to.be.lte(20)
      })

    cy.get('#launch-list').its('length').should('be.gte', 1).and('be.lt', 20)
    cy.contains('button', 'Load More').should('not.exist')
  })
})

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