expect() for BDD assertions in Cypress

Introduction

We use expect() to check if something in our app works as we want. It helps us catch mistakes early.

To check if a button is visible on the page.

To verify if a text appears after clicking a link.

To confirm a number value is correct after a calculation.

To test if a list contains the expected items.

To make sure a form input has the right value.

Syntax

Cypress

expect(actualValue).to.be.expectedCondition(expectedValue)

actualValue is what you get from your app.

expectedCondition is what you want to check, like equal, contain, or be.visible.

Examples

Checks if the number 5 is equal to 5.

Cypress

expect(5).to.equal(5)

Checks if the string 'Hello' contains 'ell'.

Cypress

expect('Hello').to.contain('ell')

Checks if the value is true.

Cypress

expect(true).to.be.true

Checks if the button is visible on the page.

Cypress

cy.get('button').then(($button) => {
  expect($button).to.be.visible
})

Sample Program

This test opens a page and checks if the main heading text is exactly 'Kitchen Sink'.

Cypress

describe('My First Test', () => {
  it('checks if the heading is correct', () => {
    cy.visit('https://example.cypress.io')
    cy.get('h1').then(($heading) => {
      expect($heading.text()).to.equal('Kitchen Sink')
    })
  })
})

Important Notes

Always use expect() inside a test to make sure your app behaves as expected.

Use clear and simple conditions to keep tests easy to understand.

Remember that expect() works well with Cypress commands that return values.

Summary

expect() helps check if your app works right.

Use it to compare actual results with what you want.

It makes tests clear and easy to read.

Practice

1. What is the main purpose of using expect() in Cypress tests?

easy

A. To log messages in the console

B. To run the test suite faster

C. To select elements on the page

D. To check if the actual value matches the expected value

Solution

1. Step 1: Understand the role of expect()

   expect() is used to compare actual results with expected results in tests.

2. Step 2: Identify the correct purpose

   It helps verify if the app behaves as expected by checking values.

3. Final Answer:

   To check if the actual value matches the expected value -> Option D

4. Quick Check:

   expect() compares values [OK]

Hint: Remember: expect() checks actual vs expected values [OK]

Common Mistakes:

• Thinking expect() runs tests
• Confusing expect() with element selectors
• Using expect() to log messages

2. Which of the following is the correct syntax to assert that a variable count equals 5 using expect() in Cypress?

easy

A. expect(count).to.equal(5);

B. expect(count).toBe(5);

C. expect(count).equals(5);

D. expect(count).is(5);

Solution

1. Step 1: Recall Cypress BDD assertion syntax

   Cypress uses Chai assertions where to.equal() checks equality.

2. Step 2: Identify the correct syntax

   expect(count).to.equal(5); is the correct way to assert equality.

3. Final Answer:

   expect(count).to.equal(5); -> Option A

4. Quick Check:

   Use to.equal() for equality [OK]

Hint: Use to.equal() for equality checks in Cypress [OK]

Common Mistakes:

• Using toBe() which is Jest syntax
• Using equals() without to
• Using is() which is invalid

3. What will be the result of this Cypress assertion?

const title = 'Welcome';
expect(title).to.have.length(7);

medium

A. Test passes because 'Welcome' has 7 characters

B. Test fails because length is checked incorrectly

C. Syntax error due to wrong method

D. Test passes but length is 6

Solution

1. Step 1: Check the string length

   The string 'Welcome' has exactly 7 characters.

2. Step 2: Understand the assertion

   to.have.length(7) correctly asserts the string length is 7.

3. Final Answer:

   Test passes because 'Welcome' has 7 characters -> Option A

4. Quick Check:

   String length 7 matches assertion [OK]

Hint: Count characters to verify length assertions [OK]

Common Mistakes:

• Assuming length counts words, not characters
• Confusing length with array length
• Using wrong assertion method

4. Identify the error in this Cypress assertion:

expect(user.name).to.equals('Alice');

medium

A. Missing parentheses after user.name

B. Incorrect method name; should be to.equal

C. Should use expect(user).to.equal('Alice')

D. No error; assertion is correct

Solution

1. Step 1: Check the assertion method

   The correct Chai assertion method is to.equal, not to.equals.

2. Step 2: Confirm syntax correctness

   Using to.equals causes a runtime error because it is not defined.

3. Final Answer:

   Incorrect method name; should be to.equal -> Option B

4. Quick Check:

   Use to.equal, not to.equals [OK]

Hint: Remember: method is to.equal, not to.equals [OK]

Common Mistakes:

• Using to.equals instead of to.equal
• Confusing property access syntax
• Assuming expect needs parentheses after property

5. You want to check that an array items contains the string 'apple' using expect(). Which assertion correctly tests this?

hard

A. expect(items).to.equal('apple');

B. expect(items).to.have.length('apple');

C. expect(items).to.include('apple');

D. expect(items).to.contain.length('apple');

Solution

1. Step 1: Understand the goal

   You want to check if 'apple' is inside the array items.

2. Step 2: Choose the correct assertion

   to.include('apple') checks if the array contains that element.

3. Final Answer:

   expect(items).to.include('apple'); -> Option C

4. Quick Check:

   Use to.include() to check array contents [OK]

Hint: Use to.include() to check if array has an item [OK]

Common Mistakes:

• Using to.equal() which checks full equality
• Using length assertions incorrectly
• Combining contain and length wrongly