As a developer, mastering testing frameworks like Capybara is a must if you want to build robust, stable web applications. During job interviews, expect questions that evaluate your knowledge of Capybara’s features and how to leverage them for writing automated tests.
This comprehensive guide covers the 25 most common Capybara interview questions that recruiters ask. I’ll explain each query in simple terms along with sample answers to help you ace your next technical interview. Let’s dive in!
1. What is Capybara and what problems does it solve?
Capybara is an open-source Ruby library used for automating web application testing. It simulates how real users interact with your app by mimicking actions like filling forms, clicking buttons, following links etc.
Capybara solves several problems in testing web apps:
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It abstracts away browser complexities by providing a clean DSL (domain-specific language).
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Its API simulates actual user behavior, allowing for acceptance and integration testing.
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It handles JS web apps efficiently by managing asynchronous actions
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You can switch backend drivers like Selenium without changing tests
2. What are the key benefits of using Capybara for testing?
Some major benefits of using Capybara are:
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Intuitive DSL that is easy to read and write.
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Supports multiple drivers like Selenium, RackTest, Webkit.
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Automatic synchronization of asynchronous actions.
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Powerful element identification techniques like CSS, XPath.
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Inbuilt support for frameworks like RSpec and Cucumber.
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Handling of JS popups and prompts.
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Great community support.
3. What are the prerequisites for using Capybara?
To use Capybara, you need:
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Ruby 2.2.2 or higher installed. Capybara 3.33 requires at least Ruby 2.4.
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The Capybara gem added to your project.
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A testing framework like RSpec, Cucumber, Minitest.
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A backend driver like Selenium or RackTest installed and configured.
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For JS testing, a headless browser like Poltergeist or PhantomJS.
4. How does Capybara compare to Selenium or Watir?
While Selenium and Watir allow web automation, Capybara aims to provide a high-level API that is natural to read and write. It has a more rich and expressive DSL compared to Selenium and Watir.
It is also driver agnostic, so you can easily switch the underlying Selenium, Webkit drivers. This abstraction is missing in Selenium and Watir.
Capybara also handles synchronization of asynchronous actions elegantly. Overall, Capybara sits on top of these tools to provide an easier automation interface.
5. What are the different actions you can simulate in Capybara?
Here are some common actions you can simulate in Capybara:
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Visit a webpage using
visit '/url'. -
Click on links, buttons using
click_link('Home'). -
Interact with forms using
fill_in,select,chooseetc. -
Scroll page using
execute_script('window.scrollTo(0,100)'). -
Trigger keyboard actions like
page.send_keys :space. -
Interact with popups
accept_alert{ click_link(‘Trigger Popup’) }. -
Assert for content/elements using
have_content,have_selectoretc.
6. How do you locate elements in Capybara?
Capybara provides a rich API for locating elements:
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Use CSS selectors like
find('table#users') -
XPath selectors like
find(:xpath, '//table[@id="users"]') -
Button/link text like
click_link('Home') -
Form labels like
choose('Male') -
Query using
has_selector? -
Within specific sections using
within
7. How can you access the page title in Capybara?
page.title returns the current page title. So you can access and assert on it like:
puts page.title # print titleexpect(page.title).to eq('My App') #assertion8. How do you handle iframes in Capybara?
To handle iframes, Capybara provides an within_frame method. For example:
within_frame('iframeName') do # actions to perform inside iframeendYou can also use XPath to locate the iframe element directly.
9. What are the different waiting/synchronization methods in Capybara?
Capybara handles waiting intelligently for elements to appear. You can also control waits:
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Implicit waiting using
findorhas_selector? -
Explicit wait with
using_wait_time 10 do -
page.document.synchronizemethod -
Custom JS wait like
page.has_no_css?('.busy')
10. How can you debug issues in Capybara tests?
Useful methods for debugging Capybara tests:
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save_and_open_pageto view current state of the page. -
page.driver.browser.manage.logsto access browser logs. -
binding.pryto pause execution and step through. -
Run with
--verboseflag to get more info. -
Use screenshot capturing utilities like Capybara-Screenshot.
11. How are asynchronous actions handled in Capybara?
Capybara is designed to handle asynchronous actions gracefully. For example:
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Methods like
has_selector?andhas_no_selector?wait until the result is true. -
findwaits for the element to appear. -
click_linkwaits for page load after clicking.
You can also increase the max wait time if needed.
12. How can you configure Capybara’s driver and options?
The driver and options can be configured in your test setup file like spec_helper.rb:
Capybara.default_driver = :seleniumCapybara.javascript_driver = :webkitCapybara.default_max_wait_time = 10 Capybara.app_host = 'http://localhost:3000'Drivers like :rack_test and :selenium are commonly used.
13. What is the difference between Capybara and Selenium?
While Selenium provides web application automation, Capybara is built on top of it to provide:
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An intuitive domain-specific language focused on behavior, not just browser actions.
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Synchronization of asynchronous JavaScript actions.
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Support for both CSS and XPath selectors.
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A rack-test driver for fast, headless testing of web apps without JS.
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Integration with testing frameworks like RSpec and Cucumber.
14. What are some best practices when using Capybara?
Some best practices when using Capybara:
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Use clear, descriptive test names like
it 'logs in successfully' -
Implement page objects to encapsulate page details
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Prefer CSS over complex XPath queries
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Leverage helpers for common actions like login
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Keep tests short, isolated and focused
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Avoid timeouts, sleeps as much as possible
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Use
:transactionDatabaseCleaner strategy
15. What are some common issues faced when using Capybara?
Some common issues faced:
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Flaky tests due to race conditions
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Timeouts due to long-running asynchronous actions
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Hard to debug failures due to lack of visibility into browser state
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Tests running significantly slower than expected
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Cryptic error messages that are hard to decipher
16. How can you improve the performance of Capybara tests?
Some ways to improve Capybara tests performance:
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Use
:rack_testdriver for non-JS tests. It’s faster than Selenium. -
Enable browser caching to avoid reloading static assets.
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Run a single Selenium instance and reuse across tests.
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Limit the number of visible elements on test pages.
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Set
Capybara.default_max_wait_timeappropriately. -
Use
:transactionDatabaseCleaner strategy.
17. What is the use of within in Capybara and when is it useful?
within allows you to scope actions within a specific section of the page. For example:
within('#navigation') do click_link 'About'endThis clicks the ‘About’ link only within the #navigation section.
It helps prevent ambiguities when multiple elements match a selector.
18. How can you access CSS styles of elements in Capybara?
The style
What we’re going to do
One of the biggest challenges in getting started with testing is just that—the simple act of getting started. If you’re reading this, I want you to get a small but important “win” as soon as possible. You will have written your first test for a Rails app by the end of this chapter, even if you have never done it before.
Here’s what we’re going to do:
- Start up a Rails app that is as simple as possible. Make one static page that just says “Hello, world!” Write one test (using RSpec and Capybara) that makes sure our static page really does say “Hello, world!”
The goal here is just to walk through the motions of writing a test. The test itself is rather pointless. I most likely would never write a test that only checks the content of a static page in real life. But the point isn’t to make a real test; it’s to give you a mental “Lego brick” that you can later put together with other mental Lego bricks. Writing tests get really hard very quickly, so I think it’s helpful to start with something that’s almost too easy to be true.
Run the “rails new” command
First we’ll initialize this Rails app using the good old rails new command.
You may be familiar with the -T flag. This flag means “no tests”. We would have gotten a Rails app with MiniTest tests in the test directory if we had run rails new hello_world without the -T flag. I want to use RSpec, so I want us to start with no MiniTest.
Let’s also create our application’s database at this point since we’ll have to do that eventually anyway.
This is the step where RSpec and Capybara will start to come into the picture. Each library will be included in our application in the form of a gem. We’ll also include the webdrivers gem which is necessary in order for Capybara to interact with the browser.
Let’s add the following to our Gemfile under the :development, :test group. I’ve added a comment next to each gem or group of gems describing its role. Even with the comments, it may not be abundantly clear at this moment what each gem is for. After the exercise is over, we’ll take a moment to review which library made the last step possible.
Don’t forget to bundle install.
Although we’ve already installed the RSpec gem, we haven’t installed RSpec into our application. For example, to install the Devise gem, we need to do two things: add devise to our Gemfile and run rails g devise:install. The same is true for installing RSpec. After we run this command we’ll have a spec directory in our application containing a couple config files.
Now that we’ve gotten the “plumbing” work out of the way, let’s write some actual application code.
I interviewed animals with a tiny mic again
FAQ
What is capybara testing?
What is the wait method in capybara?
Why use capybara?
Does capybara use selenium?
How does capybara work?
Capybara can talk with many different drivers who execute your tests through the same clean and simple interface. You can seamlessly choose between Selenium, Webkit, or pure Ruby drivers. Capybara automatically waits for your content to appear on the page, you never have to issue any manual periods of sleep.” A Sample Capybara Feature:
How do capybaras communicate?
Communication is vital for their social dynamics, and capybaras use a variety of vocalizations, body postures, and olfactory cues to convey messages and maintain social order. Capybaras are herbivores and have a diet primarily composed of vegetation.
What is capybara in Ruby?
First, let’s start with definitions. What is Capybara? On Capybara’s official page it is described as follows: “ Capybara is a library written in the Ruby programming language which makes it easy to simulate how a user interacts with your application.
How big does a capybara get?
The capybara ( Hydrochoerus hydrochaeris ) is the largest living rodent in the world, growing up to about 1.3 metres (4.3 feet) long and weighing up to 79 kg (174 pounds). The lesser capybara ( H. isthmius) is smaller, growing to about 1 metre (about 3 feet) in length and weighing about 28 kg (62 pounds).
