Cypress vs Selenium

Cypress vs Selenium

This article shows you the differences between Selenium library and Cypress framework. Cypress is a modern end to end testing library – a competitor of Selenium. I recommend you to get familiar with the general description of Cypress and description of Selenium problems. I wrote about it earlier (http://www.diwebsity.com/2019/07/16/why-choose-cypress/). 

Below is a table with a comparison between these two approaches (libraries) line by line for each category. I tried to be as objective as possible. This table is intended to be a help for your decision process.

Cypress vs Selenium – Comparision


SeleniumCypress
TypeIt is simply one purpose library with a strong community and additional packages. Complete framework using many front end test libraries.
LanguagesC#
Java
Java Script
TypeScript
Python
Ruby
Perl
PHP
Haskell
Objective-C
R
Dart
Elixir
JavaScript
TypeScript
SelectorsId
ClassName
CSS selectors
XPath
By text and text fragments
CSS selectors
By text and text fragments
By regex
Selecting a unique elementThere is a problem with uniqueness. When there are many elements matching a particular selector, then the first one will be returned without any notice. Trying to select a single element with not a unique selector will result in an error. This is good because it gives instant feedback about the test inaccuracy.
Browsers Multiple browser testsChrome
Opera
Firefox
Safari
Internet Explorer

Support of mobile browsers testing and testing on the browsers grind in the cloud (e.g. Browserstack or Appium)
Chrome
Chromium
Electron
DebuggingDepends on language:
C#, Java tests are executed in a synchronous way, so it is easy to debug code the same as regular programming code.
However, JavaScript and TypeScript tests are executed asynchronously, which makes the debugging very problematic.
Very good with time travel option in UI. Tests are executed in special chrome browser version with test steps explorer and preview window. It allows to select a particular step in the test case and see the state of a page at the time of executing this step.
Waiting for async operationsWith additional libraries.
Selenium doesn’t wait for any actions. It doesn’t have knowledge about any async operations.
However, there exist support libraries to handle all kind of waiting for popular frontend frameworks.
Automatically.
Cypress is run under the same browser process, so it knows when Java Script code is working. In that way it can automatically wait for finishing all front-end processing before going on with test execution.
SpeedFast
All web page operations have a small delay due to the driver working as a proxy between test instructions and browser.
Very fast
It operates on the same process in the browser.
Cross application testingYes
You can freely navigate from one application to any other URL
No
You can test only a single domain and any number of subdomain inside one domain.
Integration with CIPossible
You can use any testing library, test reports, and execution patterns. You can easily adjust it to your needs.
Possible
Using command line and npm library – Mocha
This is the only one option.
The CI service has to support npm. Today almost all of them support it.
Test recording on the CI server is a paid option for a high number of recordings.
ParallelizationYes, easilyYes, from version 3.1.0
Test confidence levelHigh
Selenium stimulates the same actions as a user.
Medium
Let more actions than a user can perform. Especially it let to perform all actions (also disabled in UI) using { force: true } which make the tests more flexible but less reliable in the context of repeating user actions.
TroubleshootingCustom-developed
We have to manage it manually. We can take screenshots, detailed error information or call stacks.
Very easy
Cypress offer UI to debug tests with the time travel option (the ability to choose particular test instruction and see, how the tested page looks before this line execution). It also supports test recording and taking screenshots.
DocumentationMedium
Base documentation is medium, but there are plenty of learning resources on the internet
Good
Work with custom elementsNeed custom code
There exist multiple additional libraries to work with custom controls
Need custom code
Execute JSPossible
We can do anything on the page and get elements in that way.
JS code is written as a string.
Possible
JS code can be written as code using a window object as a
base.cy.window().then(win => myCustomMethod())
IntegrationsBig number
On many places
Medium number
Centralized
https://docs.cypress.io/plugins/
Manipulate browser optionsCookie
LocalStorage
Screen Sizes
Extensions
Command-line options
Network options
Browsers extensionsYes
Can be automated
Yes
Need manual installation
General purposeEnd to end testing
Web automation
Web scraping
For both: developers and QA team
End to end testing
Mostly for developers
iframe supportYesNo
But there is an open issue for this.
Test case architectureCustom, but very flexible. You can do whatever you need.Hard
It is hard to create layered architecture to support test case readability (like in BDD test cases). That’s because selected elements are not persistent. We can’t select element and operate on it multiple times later in code.
The code below will not work correctly:
let poemElement = cy.get('.poem1');
poemElement.get('.list-group > .list-group-item.selected')
.should('contain', 'And there is another sunshine,');     poemElement.get('.header')
.should('contain', 'Other header,')
OtherThe most important advantage of Selenium is a great community which results in a huge number of resources to learn and resolve any problems.
Additionally, there exists a lot of libraries for Selenium. It is related with the fact that Selenium is only a simple purpose library, that cannot work without additional libraries (like for test execution).
Cypress have additional features:
– the ability to mock API calls
– the ability to control network traffic speed

This is relatively young framework and we should keep an eye on its growth. It has a great potential, but also has some serious problems/blockers for some applications.
Learning resourceshttps://www.lynda.com/Selenium-tutorials/Learning-Selenium/656801-2.html
https://www.udemy.com/selenium-training/
https://docs.cypress.io

https://github.com/cypress-io/cypress-example-recipes#xhr-web-formshttps://github.com/cypress-io/testing-workshop-cypress

I hope this comparison will help you to your own assessment of the end to end test approach. Remember to fit the testing approach to your and your organization needs (skills in the team, team structure, type of applications you create, test cases inside applications), not only following the hype. Cypress is a very promising library, but still, it has some blockers which can be problematic for your need (like single domain constraint or lack of iframe testing).

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