Endurance testing is a vital non-functional technique among the various types of testing used to evaluate application stability. Users expect applications to run smoothly 24/7 without interruption or slowdowns. While functional tests check if features work, endurance testing checks if they keep working over time.

What is Endurance Testing?

Endurance testing, also known as Soak Testing, determines whether a system can sustain a significant load for an extended period.

It is a specific software testing type designed to mimic the "marathon" of real-world production use. While a standard performance testing session might last only an hour to assess immediate behavior, endurance testing typically runs for long periods or spans multiple sessions over 12-24 hours.

The core purpose is to uncover time-dependent defects, which only become visible after the software has been running continuously for a long time. Without this testing, critical issues like memory leaks might go undetected until the application crashes in production.

Objectives of Endurance Testing

The primary goals of this testing methodology are long-term reliability rather than immediate speed.

1. Verify Stability: To confirm the system does not crash or hang during extended operations. This ensures that background processes do not fail silently after running for hours.
2. Monitor Resources: To check how the system uses memory, CPU, and disk space over time. This helps identify data collection issues where the system fails to clean up unused data.
3. Validate Response Times: Ensure the application's speed remains consistent from the first hour to the last. A system should not take 1 second to load a page in the first test session and 10 seconds to load the same page in the last test session.

Also Read - What is End-to-End (E2E) Testing

Types of Endurance Testing

Endurance testing is not a "one size fits all" activity. Depending on the application's nature, different strategies are applied.

1. Constant Load (Steady State): This is the most common type, in which the system is subjected to a fixed, steady load (e.g., 1,000 concurrent users) throughout the duration. It establishes a baseline for stability.
2. Step Load: The load is gradually increased over time (e.g., adding 100 users every hour) to see how the system handles growing demand over a long period.
3. Variable/Random Load: This simulates real-world traffic patterns in which usage fluctuates (e.g., high during the day, low at night) to test the system's ability to recover during quiet periods.
4. Failover Endurance: This involves simulating a failure (e.g., a server reboot) during a test session to ensure the system can recover and continue processing without degradation.
5. Multiple Sessions All Day: Continuous synthetic monitoring runs scripted user flows at regular intervals (24/7) to proactively track application and service performance. It helps detect issues in availability and responsiveness over time. For device resource issues such as memory leaks or battery drain, you need dedicated profiling or endurance-testing tools.

Also Check Out - Different Types of Mobile App Testing

Examples of Endurance Testing

Endurance testing mimics real-life scenarios where systems cannot afford to fail.

• Banking Systems: Banks often run long-duration endurance tests to ensure their systems don’t slowly build problems throughout the day. This helps them catch issues like connection leaks or memory buildup that could cause end-of-day transactions or batch jobs to fail.
• Video Streaming: A service like Netflix might test video playback for 12-24 continuous hours, across multiple sessions, to ensure memory leaks do not cause the app to crash or buffer for users watching marathon series.
• Healthcare Monitoring: Medical devices that monitor patient vitals must run indefinitely. Endurance tests ensure these devices do not freeze or lag after weeks of continuous operation.
• eCommerce Flash Sales: Platforms test stability over a 72-hour promotional period, broken into multiple test sessions, to ensure shopping cart functionality does not degrade as millions of log entries accumulate.
• Telecommunications: Telecom providers simulate millions of concurrent calls and data across various test sessions over 48-72 hours to ensure "call drops" do not increase and network handovers (e.g., 4G to 5G) remain smooth without latency accumulation.
• Online Gaming: Multiplayer games (MMORPGs) undergo soak testing to verify that servers do not crash due to memory leaks from thousands of players interacting simultaneously for days. On mobile, it ensures the game does not overheat the device or drain the battery excessively during marathon sessions.

When to Perform Endurance Testing?

Endurance testing is resource-intensive, so it is strategically timed during the software development lifecycle (SDLC).

1. Before Major Releases: It is critical to run these tests before a new version goes live to ensure it doesn’t break after running for a full day.
2. After Infrastructure Changes: If you migrate a database or change server hardware, endurance testing confirms the new setup can handle long-term loads.
3. For 24/7 Applications: Soak testing is essential because these systems never restart. Any minor issue, like memory slowly increasing or connections not closing correctly, builds up over time, so these tests make sure the app stays stable even after running nonstop.
4. During Maintenance Cycles: If your servers are restarted weekly, endurance tests should run for at least a week to cover the full maintenance window.

How to Perform Endurance Testing: Step-by-Step Process

A Gaming Example

Conducting an effective endurance test requires careful planning to ensure the game server can handle a marathon session.

1. Define Test Objectives: Determine precisely what you are testing for. Is it server lag, player disconnects, or high ping after hours of play?
2. Environment Setup: Create a test environment that mirrors the live game server exactly. Testing on a weaker local server will not reveal how real player traffic impacts performance.
3. Plan the Load: Decide on the duration (e.g., multiple sessions across a 48-hour "Double XP" weekend) and the volume (e.g., 80% of the server’s maximum player capacity).
4. Test Execution: Run the test using automated "bots" that mimic real player actions, such as fighting, trading, and chatting. Continuous monitoring is essential to catch when the lag starts.
5. Analyze Results: Compare the game’s performance from the start of the test to the end. Look for trends like increasing latency (ping) or server memory filling up, which indicates a memory leak.

Challenges Faced During Endurance Testing

Using our gaming example, we can see that endurance testing comes with specific hurdles that teams must overcome.

1. Long Execution Time: Locking down the staging environment for multiple sessions across a 48-hour soak test means no other developers can test their patches during that time. This creates a bottleneck in the release pipeline.
2. Memory Leak Isolation: You might confirm that the game server crashes after 30 hours, but pinpointing exactly which player action, like casting a specific spell or trading an item, caused the tiny memory leak is like finding a needle in a haystack.
3. Test Environment Instability: Sometimes the "bot" scripts crash because the testing tool cannot simulate 10,000 players across multiple sessions over 2 days. If the tool fails at hour 40, you lose nearly two days of valuable data. So, leveraging a powerful tool like HeadSpin is vital.
4. Data Accumulation: A game server logging every player movement and chat message generates massive amounts of data. Over a weekend-long test, these logs can fill up the hard drive, causing the server to freeze, not because of a bug, but because it ran out of disk space.

Best Practices for Endurance Testing

To overcome challenges and get actionable data, follow these industry standards.

1. Automate Everything: Manual testing is not feasible for extended periods. Use robust automation scripts that gracefully handle errors without halting the test.
2. Monitor Garbage Collection: specifically watch "Garbage Collection" (GC) logs. If GC activity increases over time while the load stays constant, you likely have a memory leak.
3. Use Dedicated Environments: Never run endurance tests in a shared environment. The heavy load will disrupt other testers.
4. Establish a Baseline: Run a short 1-hour test first to ensure the script works perfectly before committing to multiple sessions across a 24-hour run.

Key Metrics to Monitor While Performing Endurance Testing

During the test, engineers must watch specific data points to identify potential failure.

1. Memory Usage: Ensure the memory graph remains stable and does not climb continuously. A healthy graph should look flat or "saw-toothed" (rising and falling), not a diagonal line going up.
2. Throughput: Ensure the number of transactions per second remains consistent. If the system processes fewer requests per second over time, it indicates an internal bottleneck.
3. Response Time: Confirm that it takes the same amount of time to load a page at hour 20 as it did at hour 1. Latency is often the first indicator that the system is struggling to manage long-term data.
4. CPU Utilization: Ensure the processor is not working harder to do the same amount of work later in the test.

Also Read - Key Performance Testing Metrics You Should Track

Standard Tools for Endurance Testing

Since endurance tests run for hours or days, manual testing is impossible. Teams rely on robust automation tools to sustain the load.

1. Apache JMeter: A popular open-source tool that can run complex test scenarios indefinitely. It is free to use and has a large community for support.
2. LoadRunner: An enterprise tool that provides detailed analysis and reports. It is excellent for large organizations that need deep diagnostics.
3. Gatling: A code-based tool often used in DevOps pipelines. It is preferred by developers who want to keep testing scripts alongside their application code.
4. WebLOAD: A tool known for simulating heavy user loads efficiently. It helps generate a massive load with fewer hardware resources.

Where these tools fall short: While these platforms are powerful for generating synthetic server load, they often fail to capture the physical "client-side" experience. They cannot simulate real-world variables like battery heating, network carrier throttling, or device-specific memory leaks. This is where HeadSpin bridges the gap.

It lets teams combine JMeter’s load-generation power with HeadSpin’s real-world testing and analytics. You create your JMeter test plan the way you normally would, defining thread groups, samplers, assertions, and listeners.

HeadSpin lets you import or run those JMeter tests within its platform, triggering them against real devices or real infrastructure. This pairs JMeter’s simulated load with HeadSpin’s device network and performance measurement layer so you see how your app behaves in real-world conditions.

How HeadSpin Enhances Endurance Testing

While traditional tools generate load, they often fail to capture the actual user experience on real devices over extended periods. HeadSpin addresses this gap with its AI-driven global device infrastructure.

1. Integrate With Apache JMeter: HeadSpin allows you to integrate JMeter tests directly into its platform. These tests can then be executed on real devices. This integration combines JMeter's load simulation capabilities with HeadSpin's extensive device network and performance measurement tools, providing insights into your application's behavior under realistic, real-world conditions.
2. Continuous Monitoring of 130+ KPIs: HeadSpin captures over 130 key performance indicators (KPIs), including battery usage, CPU consumption, and page load times. This deep visibility is critical for identifying resource exhaustion during long soak tests.
3. Grafana Dashboards: Use Grafana Dashboards for clear visualization and analysis of testing data, allowing swift identification and resolution of issues. Customize dashboards for different teams (e.g., network metrics for technical teams, financial KPIs for business teams). Set up Grafana alerts for notifications when performance thresholds are exceeded.
4. Regression Intelligence: Identify regressions caused by factors like code changes or updates. Analyze app performance against industry standards and KPIs. Additionally, compare the performance of different builds across multiple sessions.
5. Global Real Device Infrastructure: HeadSpin lets you run endurance tests on thousands of real, SIM-enabled (physical & eSIM) devices across 50+ locations. This ensures that your test results reflect real-world battery drain, thermal throttling, and network fluctuations that emulators cannot simulate.

Conclusion

Endurance testing is the only reliable way to ensure your application can handle the marathon of daily production use. By identifying critical issues like memory leaks and resource exhaustion early, you protect your users from unexpected crashes and sluggish performance. 

HeadSpin elevates this process by providing real device insights and AI-powered analytics, ensuring your app performs flawlessly, not just for an hour, but for days on end.

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FAQs

Q1. Can endurance testing be performed manually?

Ans: No, manual endurance testing is practically impossible and highly prone to error. It is physically demanding for a human tester to perform repetitive actions continuously for 12 to 72 hours without stopping.

Q2. How do I determine the right duration for an endurance test?

Ans: The duration should mimic your business's typical maintenance cycle or peak usage window. For example, if you restart your servers once a week, your endurance test should run for at least a week to cover that full cycle. 

Q3. What is the difference between endurance testing and scalability testing?

Ans: Endurance testing checks stability over time with a constant load, whereas scalability testing increases the load to see if the system can handle more users. Endurance focuses on "how long," while scalability focuses on "how much."