System tests with Capybara in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of system tests in Rails using Capybara?

System tests check how the whole application works from the user's point of view by simulating browser actions like clicking links and filling forms.

beginner

How do you tell Capybara to visit a page in a system test?

Use the visit method with the page path, for example: visit root_path.

beginner

Which Capybara method simulates clicking a button or link?

The click_on method simulates clicking a button or link by its text or id.

beginner

How do you fill in a form field using Capybara in a system test?

Use the fill_in method with the field label or id and the value, like fill_in 'Email', with: '[e-mail]'.

beginner

What does the assert_text method do in a Capybara system test?

It checks that the given text appears somewhere on the current page, confirming expected content is visible to the user.

Which method in Capybara is used to simulate a user visiting a page?

A assert_text

B click_on

C fill_in

D visit

The visit method tells Capybara to open a specific page URL.

How do you simulate clicking a button labeled 'Submit' in Capybara?

A click_on 'Submit'

B click_button 'Submit'

C fill_in 'Submit'

D visit 'Submit'

Both click_on and click_button methods can be used to click buttons by their text.

Which Capybara method fills in a text field in a form?

A fill_in

B click_on

C visit

D assert_text

Use fill_in to enter text into form fields.

What does assert_text 'Welcome' check in a system test?

A That a button named 'Welcome' exists

B That the page URL is 'Welcome'

C That the page contains the text 'Welcome'

D That the form field 'Welcome' is filled

assert_text verifies visible text on the page.

In Rails system tests, which driver does Capybara use by default for JavaScript support?

A Selenium

B Rack::Test

C Poltergeist

D Webkit

Capybara uses Selenium by default to support JavaScript in system tests.

Explain how you would write a simple system test with Capybara to check that a user can visit the homepage and see a welcome message.

Think about what a user does first and what they expect to see.

Describe the steps Capybara takes to simulate a user filling out and submitting a form in a system test.

Imagine you are the user typing and clicking.

Practice

1. What is the main purpose of system tests with Capybara in a Rails application?

easy

A. To test individual Ruby methods for correctness

B. To measure server response time under load

C. To check database schema migrations

D. To simulate user actions in a real browser and check app behavior

Solution

1. Step 1: Understand system tests role

   System tests simulate how a real user interacts with the app through a browser.

2. Step 2: Compare with other test types

   Unlike unit tests or performance tests, system tests focus on full app behavior with UI.

3. Final Answer:

   To simulate user actions in a real browser and check app behavior -> Option D

4. Quick Check:

   System tests = simulate user in browser [OK]

Hint: System tests mimic real user clicks and typing [OK]

Common Mistakes:

• Confusing system tests with unit tests
• Thinking system tests check only backend code
• Assuming system tests measure performance

2. Which of the following is the correct way to visit the homepage in a Capybara system test?

easy

A. navigate_to root_url

B. go_to '/'

C. visit root_path

D. open_page '/'

Solution

1. Step 1: Recall Capybara visit syntax

   Capybara uses the method visit with a path or URL to open a page.

2. Step 2: Match correct method and argument

   root_path is the Rails helper for homepage path, so visit root_path is correct.

3. Final Answer:

   visit root_path -> Option C

4. Quick Check:

   Capybara visit + path helper = visit root_path [OK]

Hint: Use 'visit' with Rails path helpers to open pages [OK]

Common Mistakes:

• Using non-existent methods like go_to or open_page
• Confusing root_path with root_url in system tests
• Forgetting to use visit before path

3. Given this system test code snippet, what will be the output on the page?

visit root_path
fill_in 'Email', with: '[e-mail]'
fill_in 'Password', with: 'secret'
click_button 'Log in'
expect(page).to have_content('Welcome, [e-mail]')

medium

A. Test passes if 'Welcome, [e-mail]' appears after login

B. Test fails because 'fill_in' cannot find fields

C. Test raises error due to missing 'visit' method

D. Test passes without checking page content

Solution

1. Step 1: Analyze test steps

   The test visits the homepage, fills in login form fields, clicks login, then checks for welcome message.

2. Step 2: Understand Capybara behavior

   If the login works and page shows the welcome text, have_content will pass and test passes.

3. Final Answer:

   Test passes if 'Welcome, [e-mail]' appears after login -> Option A

4. Quick Check:

   fill_in + click_button + have_content = success check [OK]

Hint: Check page content after actions to confirm success [OK]

Common Mistakes:

• Assuming fill_in fails without checking form existence
• Forgetting to call visit before actions
• Ignoring the expect(page).to have_content assertion

4. You wrote this system test but it fails with "Capybara::ElementNotFound" error:

visit root_path
fill_in 'Username', with: 'testuser'
click_button 'Submit'

What is the most likely cause?

medium

A. Capybara does not support fill_in method

B. The form does not have a field labeled 'Username'

C. The button 'Submit' is missing from the page

D. You forgot to call visit before fill_in

Solution

1. Step 1: Understand Capybara::ElementNotFound meaning

   This error means Capybara could not find the form field or button with given label.

2. Step 2: Check test code and error cause

   Since visit is called, the likely cause is the field labeled 'Username' does not exist on the page.

3. Final Answer:

   The form does not have a field labeled 'Username' -> Option B

4. Quick Check:

   ElementNotFound = missing field or button [OK]

Hint: Check labels exactly match form fields and buttons [OK]

Common Mistakes:

• Assuming visit was not called when it was
• Thinking Capybara lacks fill_in support
• Ignoring exact label spelling and case

5. You want to write a system test that logs in a user, visits their profile page, and verifies their username is shown. Which sequence correctly uses Capybara commands?

hard

A. visit login_path; fill_in 'Email', with: user.email; fill_in 'Password', with: user.password; click_button 'Log in'; visit profile_path(user); expect(page).to have_content(user.username)

B. fill_in 'Email', with: user.email; click_button 'Log in'; visit profile_path(user); expect(page).to have_content(user.username)

C. visit profile_path(user); fill_in 'Email', with: user.email; click_button 'Log in'; expect(page).to have_content(user.username)

D. visit login_path; click_button 'Log in'; fill_in 'Email', with: user.email; fill_in 'Password', with: user.password; expect(page).to have_content(user.username)

Solution

1. Step 1: Identify correct login flow

   You must visit the login page first, then fill in email and password, then click login.

2. Step 2: Visit profile after login and check content

   After successful login, visit the profile page and check the username is displayed.

3. Final Answer:

   visit login_path; fill_in 'Email', with: user.email; fill_in 'Password', with: user.password; click_button 'Log in'; visit profile_path(user); expect(page).to have_content(user.username) -> Option A

4. Quick Check:

   Login then visit profile then check content [OK]

Hint: Always visit pages before interacting or checking content [OK]

Common Mistakes:

• Trying to fill_in before visiting login page
• Visiting profile before logging in
• Clicking buttons before filling required fields