Debugging with Cypress vs. Playwright
When it comes to end-to-end testing, developers often face the challenging task of debugging failing tests. Two of the most popular tools in this space are Cypress and Playwright. Both offer powerful features, but Cypress excels, particularly in the realm of time travel debugging. In this blog post, we'll explore the differences in debugging between Cypress and Playwright and highlight why Cypress's approach to time travel debugging gives it a significant edge.
Debugging with Cypress
Cypress provides an intuitive and developer-friendly debugging experience, leveraging features like its built-in debugger in the open-source app and the innovative Test Replay for CI. These features accumulate into something called: Time travel debugging. And it cannot be overestimated in its ease of use. It is this feature that sets Cypress apart from the other test automation frameworks out there.
- Interactive Test Runner: Cypress's interactive test runner is a game-changer. As tests run, Cypress captures screenshots at each step and logs every action. This allows developers to hover over each command in the Command Log to see a snapshot of the application at that point. The interactive test runner is started with the following command:
npx cypress open
2. Built-In Debugger: Cypress's debugger is integrated seamlessly into the test runner. Developers can use cy.debug() to pause the test at any point, inspect the current state of the application, and step through code execution. This makes it incredibly easy to identify where things go wrong.
3. Detailed Command Log: The Command Log provides a comprehensive view of every command executed during the test. Developers can click on any command to see detailed information, including the state of the application before and after the action. This level of detail is invaluable for understanding the sequence of events that led to a test failure. If even that mountain of information proves insufficient, cy.log() allows developers to expand the printed information even more.
4. Video and screenshot recordings: While Cypress is remarkable at debugging while running the tests, let's not forget that cypress also endeavours to enable developers to debug the application without running the testing framework. This while using the multitude of videos and screenshots that Cypress can provide. The small size of these makes them perfect to add into a bug ticket.
Test Replay for CI
When tests are run in Continuous Integration (CI) environments, debugging can become more challenging due to the lack of an interactive interface. Cypress addresses this with its Test Replay feature, available in Cypress Cloud.
- Recording Test Runs: Cypress Cloud records every test run, capturing video and logs. This allows developers to see exactly what happened during a CI run, even if they weren't present.
2. Replaying Tests: With Test Replay, developers can replay test runs directly from Cypress Cloud. This includes stepping through each command and seeing the application's state, just like in the interactive test runner. This makes it significantly easier to diagnose and resolve issues that only occur in CI.
Debugging with Playwright
Playwright also offers debugging tools, but they lack the seamless integration and user-friendly experience provided by Cypress. Playwright relies a great deal on the IDE that's being used and the plugins that Microsoft offers. This ties the framework just the bit harder to the Microsoft environment. To have the best playwright experience, Visual Studio Code with it's assorted extensions is required.
- Playwright Inspector: Playwright provides an Inspector tool that allows developers to pause tests and inspect the current state of the application. While useful, it doesn't offer the same level of time travel capabilities as Cypress. In addition, there is a specific
BASHcommand required to enable the inspector:PWDEBUG=1 node my_script.js.
2. Console Logs and Tracing: Playwright relies heavily on console logs and tracing for debugging. Developers need to manually add logging statements to their tests, which can be time-consuming and less intuitive compared to Cypress's automatic capturing of test states. This tracing has to be enabled and stopped using a line of code. Example code is below this paragraph. Another way to increase logging would be to add the verbose logging in playwright: DEBUG=pw:api node my_script.js
await page.tracing.start({ screenshots: true, snapshots: true });
await page.goto('https://example.com');
await page.tracing.stop({ path: 'trace.zip' });
3. Video Recording: Playwright supports video recording of test runs, which can be helpful. However, the lack of integrated time travel debugging makes it harder to correlate specific actions with the application's state at different points.
Why Cypress is Better for Debugging
- Intuitive Time Travel Debugging: Cypress's time travel debugging is a standout feature that significantly reduces the time and effort required to diagnose and fix test failures. The ability to see the application's state at each step, coupled with an interactive command log, provides unparalleled visibility into test runs.
2. Seamless Integration: Cypress's debugging tools are seamlessly integrated into both the open-source app and Cypress Cloud. This ensures a consistent debugging experience, whether running tests locally or in CI.
3. Developer-Friendly: Cypress's focus on providing a developer-friendly experience is evident in its comprehensive debugging tools. The built-in debugger, detailed command logs, and Test Replay feature make it easy for developers to identify and resolve issues quickly.
4. Built-in debugging capabilities: While Cypress has debugging built into the basic framework, playwright required a specific plugin and specific configuration to make debugging a user-friendly experience.