Reading file contents in Cypress - Build an Automation Script

Verify contents of a text file

Preconditions (2)

Step 1: Open the test environment

Step 2: Read the contents of 'sample.txt' file using Cypress

Step 3: Verify that the file contents exactly match 'Hello, Cypress!'

✅ Expected Result: The test should confirm that the file content is 'Hello, Cypress!' and pass

Automation Requirements - Cypress

Assertions Needed:

Assert that the file content equals 'Hello, Cypress!'

Best Practices:

Use cy.fixture() to read file contents

Use .then() to handle asynchronous reading

Use strict equality assertion with .should('eq', expectedValue)

Automated Solution

Cypress

describe('Reading file contents test', () => {
  it('should read and verify the contents of sample.txt', () => {
    cy.fixture('sample.txt').then((content) => {
      expect(content).to.eq('Hello, Cypress!')
    })
  })
})

This test uses cy.fixture() to read the file sample.txt from the cypress/fixtures folder.

The .then() callback handles the asynchronous file read and receives the file content as content.

We then use expect(content).to.eq('Hello, Cypress!') to assert the content exactly matches the expected string.

This approach follows Cypress best practices for reading files and making assertions.

Common Mistakes - 3 Pitfalls

Using cy.readFile() without specifying the correct path

Not handling the asynchronous nature of file reading

{'mistake': "Using loose equality assertions like .should('contain', expectedValue) when exact match is needed", 'why_bad': 'The test may pass even if the file content has extra unexpected text.', 'correct_approach': "Use strict equality assertions like .should('eq', expectedValue) or expect().to.eq()"}

Bonus Challenge

Now add data-driven testing to verify contents of three different files: 'sample1.txt', 'sample2.txt', and 'sample3.txt' with expected contents 'Hello, Cypress!', 'Test File 2', and 'Final File Content' respectively.

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