Common Loading States Bugs and How to Catch Them

Loading states bugs are a common issue in web and mobile applications, often leading to poor user experiences and potential loss of users. These bugs can manifest in various forms, from delayed respon

Common Loading States Bugs and How to Catch Them

Loading states bugs are a common issue in web and mobile applications, often leading to poor user experiences and potential loss of users. These bugs can manifest in various forms, from delayed responses to infinite spinners, and they can be challenging to catch and fix. This guide will explore the most common loading states bugs, why they occur, how they appear to users, and how to reproduce, detect, and fix them. We'll also discuss how persona-driven autonomous exploration can help surface these issues that scripted tests might miss.

Understanding Loading States Bugs

What Are Loading States Bugs?

Loading states bugs occur when the application fails to handle the intermediate states between user actions and the completion of those actions. These bugs can cause the application to hang, display incorrect or incomplete data, or exhibit other unexpected behaviors. Common scenarios include slow network conditions, server delays, and client-side issues.

Why Do Loading States Bugs Happen?

1. Network Latency: Slow or unreliable network connections can cause delays in data fetching, leading to poor user experience.
2. Server Performance: Overloaded servers or inefficient server-side code can result in slow responses or timeouts.
3. Client-Side Issues: Mismanaged state, inefficient data handling, or incorrect error handling on the client side can cause loading states to break.
4. Third-Party Services: Dependency on third-party services that are slow or unreliable can introduce delays.

Common Loading States Bugs

1. Infinite Spinners

#### Symptom

Users are presented with a loading spinner that never stops, indicating that the application is stuck in a loading state.

#### Why It Happens

• Network Issues: The request to the server times out or the server never responds.
• Client-Side Errors: The loading state is not properly managed, and the application fails to update the UI when the data is received.

#### How to Reproduce

• Simulate Slow Network: Use tools like Charles Proxy or Network Link Conditioner to simulate slow network conditions.
• Server Delays: Introduce artificial delays on the server side to mimic slow responses.

#### How to Detect

• Manual Testing: Test the application under slow network conditions and observe the loading states.
• Automated Testing: Use tools like Selenium or Cypress to simulate slow network conditions and check for infinite spinners.

#### How to Fix

• Timeout Handling: Implement timeouts for network requests to prevent infinite waiting.
• Error Handling: Ensure that the application properly handles errors and updates the UI accordingly.
• State Management: Use state management libraries like Redux (for React) or Vuex (for Vue) to manage loading states effectively.

2. Blank Screens

#### Symptom

Users see a blank screen or a partially loaded page, often due to a failure in data fetching or rendering.

#### Why It Happens

• Data Fetching Errors: The application fails to fetch the required data from the server.
• Rendering Issues: The application fails to render the data correctly, leading to a blank screen.

#### How to Reproduce

• Simulate Network Errors: Use tools to simulate network errors or data fetching failures.
• Server Errors: Introduce errors on the server side to test how the application handles them.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the UI.
• Automated Testing: Use tools like Appium for mobile or Playwright for web to simulate these conditions and check for blank screens.

#### How to Fix

• Error Handling: Implement robust error handling to ensure that the application can recover from data fetching errors.
• Fallback Content: Provide fallback content or error messages to inform users when data cannot be loaded.

3. Stale Data

#### Symptom

Users see outdated or incorrect data, often due to the application failing to refresh the data.

#### Why It Happens

• Caching Issues: The application caches data incorrectly, leading to stale data being displayed.
• Data Synchronization: The application fails to synchronize data with the server, causing outdated data to be shown.

#### How to Reproduce

• Simulate Caching: Use browser developer tools to simulate caching scenarios.
• Server-Side Changes: Make changes on the server side to test how the application handles data updates.

#### How to Detect

• Manual Testing: Test the application by making changes on the server side and observing the UI.
• Automated Testing: Use tools like Cypress to automate these tests and ensure that the application refreshes data correctly.

#### How to Fix

• Cache Management: Implement proper cache management strategies to ensure that data is refreshed when necessary.
• Data Synchronization: Use techniques like WebSockets or server-sent events to keep the client-side data in sync with the server.

4. Flash of Unstyled Content (FOUC)

#### Symptom

Users briefly see unstyled content before the styles are applied, leading to a jarring user experience.

#### Why It Happens

• CSS Loading: The application fails to load CSS files quickly enough, causing unstyled content to be displayed.
• JavaScript Execution: Delays in JavaScript execution can cause styles to be applied after the content is rendered.

#### How to Reproduce

• Simulate Slow Network: Use tools to simulate slow network conditions and observe the loading process.
• Delay JavaScript Execution: Introduce delays in JavaScript execution to test how the application handles it.

#### How to Detect

• Manual Testing: Test the application under slow network conditions and observe the loading process.
• Automated Testing: Use tools like Lighthouse to simulate slow network conditions and check for FOUC.

#### How to Fix

• Critical CSS: Use critical CSS to ensure that essential styles are loaded first.
• Optimize JavaScript: Optimize JavaScript execution to ensure that styles are applied quickly.

5. Double Loading

#### Symptom

Users see the content being loaded twice, often due to the application making redundant requests.

#### Why It Happens

• Multiple Requests: The application makes multiple requests for the same data, leading to double loading.
• State Management: Poor state management can cause the application to re-fetch data unnecessarily.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate network conditions and observe the loading process.
• State Changes: Introduce state changes to test how the application handles data fetching.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the loading process.
• Automated Testing: Use tools like Postman to simulate multiple requests and check for double loading.

#### How to Fix

• Request Management: Implement request management to ensure that the application does not make redundant requests.
• State Management: Use state management libraries to manage data fetching and prevent double loading.

6. Loading Spinner Disappears Too Early

#### Symptom

The loading spinner disappears before the data is fully loaded, leading to a poor user experience.

#### Why It Happens

• Premature State Updates: The application updates the loading state before the data is fully loaded.
• Asynchronous Issues: Asynchronous operations are not properly managed, leading to premature updates.

#### How to Reproduce

• Simulate Slow Network: Use tools to simulate slow network conditions and observe the loading process.
• Artificial Delays: Introduce artificial delays to test how the application handles asynchronous operations.

#### How to Detect

• Manual Testing: Test the application under slow network conditions and observe the loading process.
• Automated Testing: Use tools like Cypress to simulate slow network conditions and check for premature state updates.

#### How to Fix

• Proper State Management: Ensure that the loading state is only updated when the data is fully loaded.
• Asynchronous Handling: Use techniques like Promises or async/await to handle asynchronous operations correctly.

7. Loading States in Modal Dialogs

#### Symptom

Users see modal dialogs that fail to display loading states, leading to a poor user experience.

#### Why It Happens

• Modal Implementation: The modal dialog implementation does not properly handle loading states.
• State Management: The application fails to manage the state of the modal dialog correctly.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate slow network conditions and observe the modal dialog.
• Server Delays: Introduce delays on the server side to test how the modal dialog handles loading states.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the modal dialog.
• Automated Testing: Use tools like Selenium to simulate these conditions and check for loading states in modal dialogs.

#### How to Fix

• Modal Implementation: Ensure that the modal dialog implementation properly handles loading states.
• State Management: Use state management libraries to manage the state of the modal dialog effectively.

8. Loading States in Infinite Scrolling

#### Symptom

Users see infinite scrolling that fails to load new content, leading to a poor user experience.

#### Why It Happens

• Network Issues: The application fails to fetch new content due to network issues.
• State Management: The application fails to manage the state of the infinite scrolling correctly.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate slow network conditions and observe the infinite scrolling.
• Server Delays: Introduce delays on the server side to test how the infinite scrolling handles loading states.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the infinite scrolling.
• Automated Testing: Use tools like Cypress to simulate these conditions and check for loading states in infinite scrolling.

#### How to Fix

• Network Handling: Implement proper network handling to ensure that the application can fetch new content even under slow network conditions.
• State Management: Use state management libraries to manage the state of the infinite scrolling effectively.

9. Loading States in Lazy Loading

#### Symptom

Users see lazy-loaded content that fails to load, leading to a poor user experience.

#### Why It Happens

• Network Issues: The application fails to fetch the lazy-loaded content due to network issues.
• State Management: The application fails to manage the state of the lazy-loaded content correctly.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate slow network conditions and observe the lazy loading.
• Server Delays: Introduce delays on the server side to test how the lazy loading handles loading states.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the lazy loading.
• Automated Testing: Use tools like Playwright to simulate these conditions and check for loading states in lazy loading.

#### How to Fix

• Network Handling: Implement proper network handling to ensure that the application can fetch lazy-loaded content even under slow network conditions.
• State Management: Use state management libraries to manage the state of the lazy-loaded content effectively.

10. Loading States in Background Processes

#### Symptom

Users see background processes that fail to update the UI, leading to a poor user experience.

#### Why It Happens

• Background Process Management: The application fails to properly manage background processes and update the UI accordingly.
• State Management: The application fails to manage the state of the background processes correctly.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate slow network conditions and observe the background processes.
• Server Delays: Introduce delays on the server side to test how the background processes handle loading states.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the background processes.
• Automated Testing: Use tools like Appium to simulate these conditions and check for loading states in background processes.

#### How to Fix

• Background Process Management: Ensure that the application properly manages background processes and updates the UI accordingly.
• State Management: Use state management libraries to manage the state of the background processes effectively.

11. Loading States in Form Submissions

#### Symptom

Users see form submissions that fail to provide feedback, leading to a poor user experience.

#### Why It Happens

• Network Issues: The application fails to submit the form due to network issues.
• State Management: The application fails to manage the state of the form submission correctly.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate slow network conditions and observe the form submissions.
• Server Delays: Introduce delays on the server side to test how the form submissions handle loading states.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the form submissions.
• Automated Testing: Use tools like Cypress to simulate these conditions and check for loading states in form submissions.

#### How to Fix

• Network Handling: Implement proper network handling to ensure that the application can submit forms even under slow network conditions.
• State Management: Use state management libraries to manage the state of the form submissions effectively.

12. Loading States in Multi-Step Processes

#### Symptom

Users see multi-step processes that fail to provide feedback, leading to a poor user experience.

#### Why It Happens

• Network Issues: The application fails to complete multi-step processes due to network issues.
• State Management: The application fails to manage the state of the multi-step processes correctly.

#### How to Reproduce

• Simulate Network Conditions: Use tools to simulate slow network conditions and observe the multi-step processes.
• Server Delays: Introduce delays on the server side to test how the multi-step processes handle loading states.

#### How to Detect

• Manual Testing: Test the application under various network conditions and observe the multi-step processes.
• Automated Testing: Use tools like Playwright to simulate these conditions and check for loading states in multi-step processes.

#### How to Fix

• Network Handling: Implement proper network handling to ensure that the application can complete multi-step processes even under slow network conditions.
• State Management: Use state management libraries to manage the state of the multi-step processes effectively.

Test Matrix for Loading States Bugs

Manual and Automated Approaches

Manual Testing

#### Benefits

• Flexibility: Manual testing allows testers to explore the application in a more flexible and exploratory manner.
• User Perspective: Manual testing provides a better understanding of the user experience and can help identify issues that automated testing might miss.

#### Challenges

• Time-Consuming: Manual testing can be time-consuming, especially for large and complex applications.
• Reproducibility: It can be challenging to reproduce specific conditions and scenarios consistently.

#### Tools

• Browser Developer Tools: Use browser developer tools to simulate network conditions, inspect network requests, and manage state.
• Network Link Conditioner: Use tools like Network Link Conditioner to simulate slow network conditions on mobile devices.
• Charles Proxy: Use Charles Proxy to simulate network conditions and inspect HTTP requests.

Automated Testing

#### Benefits

• Reproducibility: Automated tests can be run consistently and repeatedly, ensuring that the same conditions and scenarios are tested each time.
• Speed: Automated tests can be run quickly and efficiently, covering a large number of scenarios in a short amount of time.

#### Challenges

• Setup and Maintenance: Setting up and maintaining automated tests can be complex and time-consuming.
• Coverage: Automated tests might not cover all possible scenarios and edge cases, especially those that only show up in production.

#### Tools

• Selenium: Use Selenium for automating web applications and testing loading states.
• Cypress: Use Cypress for end-to-end testing and simulating network conditions.
• Playwright: Use Playwright for cross-browser testing and simulating network conditions.
• Appium: Use Appium for automating mobile applications and testing loading states.

Persona-Driven Autonomous Exploration

Persona-driven autonomous exploration is a powerful approach to testing that can help surface loading states bugs that scripted tests might miss. SUSA (SUSATest) is an autonomous QA platform that explores the application itself, handling various user personas and behavior profiles.

#### Benefits

• Comprehensive Coverage: SUSA can explore a wide range of scenarios and edge cases, ensuring comprehensive coverage.
• No Scripts Needed: SUSA does not require manual scripting, making it easier to set up and maintain.
• User Personas: SUSA uses a range of user personas (curious, impatient, novice, adversarial, elderly, accessibility, power user, and others) to test the application from different perspectives.
• Cross-Session Learning: SUSA remembers explored screens and dead ends, making each run smarter and more efficient.

#### How to Use SUSA

1. Upload APK or Point to Web URL: Upload your APK file or point SUSA to your web URL.
2. Run Exploration: SUSA will explore the application, handling various user personas and behavior profiles.
3. Review Results: SUSA will identify crashes, ANRs, dead buttons, accessibility violations, security issues, and UX friction.
4. Auto-Generated Regression Scripts: SUSA will auto-generate regression scripts (Appium for Android, Playwright for Web) from what it discovered.

Real Examples and Edge Cases

#### Example 1: Infinite Spinners in a Mobile App

Scenario: A mobile app for booking flights displays an infinite spinner when the user tries to search for flights under slow network conditions.

Reproduction:

• Simulate Slow Network: Use Network Link Conditioner on an iOS device to simulate slow network conditions.
• Trigger Search: Initiate a flight search and observe the spinner.

Detection:

• Manual Testing: Observe the spinner and ensure it does not disappear prematurely.
• Automated Testing: Use Appium to simulate the search and check for the spinner.

Fix:

• Timeout Handling: Implement a timeout for the search request to prevent infinite waiting.
• Error Handling: Display an error message if the search fails to complete within the timeout period.

#### Example 2: Blank Screens in a Web Application

Scenario: A web application for managing customer orders displays a blank screen when the user tries to load the order details page under slow network conditions.

Reproduction:

• Simulate Slow Network: Use Charles Proxy to simulate slow network conditions.
• Load Order Details: Navigate to the order details page and observe the screen.

Detection:

• Manual Testing: Observe the screen and ensure it does not remain blank.
• Automated Testing: Use Cypress to simulate the network conditions and check for a blank screen.

Fix:

• Error Handling: Implement robust error handling to ensure the application can recover from data fetching errors.
• Fallback Content: Provide fallback content or error messages to inform users when data cannot be loaded.

#### Example 3: Stale Data in a Multi-Step Process

Scenario: A multi-step process for creating a new account in a web application displays stale data when the user navigates back to a previous step.

Reproduction:

• Simulate Server-Side Changes: Make changes on the server side to test how the application handles data updates.
• Navigate Back: Navigate back to a previous step in the multi-step process and observe the data.

Detection:

• Manual Testing: Test the application by making server-side changes and observing the UI.
• Automated Testing: Use Playwright to automate the multi-step process and check for stale data.

Fix:

• Data Synchronization: Use techniques like WebSockets or server-sent events to keep the client-side data in sync with the server.

Checklist for Catching Loading States Bugs

1. Simulate Slow Network Conditions: Use tools like Network Link Conditioner, Charles Proxy, or Lighthouse to simulate slow network conditions.
2. Test Under Various Network Conditions: Test the application under different network conditions, including slow, fast, and unreliable connections.
3. Implement Robust Error Handling: Ensure that the application can handle errors gracefully and provide useful feedback to users.
4. Use State Management Libraries: Use state management libraries like Redux or Vuex to manage loading states effectively.
5. Test Multi-Step Processes: Ensure that multi-step processes handle loading states correctly and provide feedback to users.
6. Test Background Processes: Ensure that background processes update the UI correctly and provide feedback to users.
7. Test Modal Dialogs: Ensure that modal dialogs handle loading states correctly and provide feedback to users.
8. Test Form Submissions: Ensure that form submissions handle loading states correctly and provide feedback to users.
9. Test Infinite Scrolling and Lazy Loading: Ensure that infinite scrolling and lazy loading handle loading states correctly and provide feedback to users.
10. Use Persona-Driven Autonomous Exploration: Use tools like SUSA to explore the application from different user perspectives and catch edge cases.

Takeaways

1. Loading states bugs can significantly impact user experience and lead to user churn. It is crucial to identify and fix these issues before release.
2. Common loading states bugs include infinite spinners, blank screens, stale data, and more. Each bug has specific causes and can be reproduced, detected, and fixed using the right approaches and tools.
3. Manual and automated testing both have their benefits and challenges. Combining both approaches can provide comprehensive coverage.
4. Persona-driven autonomous exploration can help surface loading states bugs that scripted tests might miss, ensuring a more robust and user-friendly application.

By following the guidelines and best practices outlined in this guide, you can effectively catch and fix loading states bugs, leading to a better user experience and a more reliable application.