What is Endurance Testing and How to Do It Right

Software systems are no longer built for short bursts of interaction—they’re expected to run continuously, 24/7, supporting users across time zones, industries, and critical operations. But what happens when your application performs well in the first hour, then crashes after eight? Or begins to leak memory after running for two days straight? These are the types of issues that endurance testing is designed to uncover—and prevent.

The stakes are high. According to the Consortium for Information & Software Quality (CISQ), software failures cost U.S. businesses over $2.41 trillion in 2022, with operational failures, such as unplanned outages and performance degradation, making up a significant share. A 2023 survey reported that 75% of tech teams struggle to maintain software performance over time, particularly under continuous usage. These challenges point to a clear need for rigorous long-duration testing strategies that can help ensure reliability far beyond initial launch.

Endurance testing plays a critical role in uncovering performance and stability issues that don’t appear in short-term functional or load tests. From online banking systems and healthcare apps to streaming platforms, software today needs to maintain consistent behavior over days, not just minutes.

In this blog post, we’ll explore what endurance testing involves, why it’s essential, and how to implement it effectively to build software that doesn’t just launch well but lasts.

Understanding endurance testing

Endurance testing—also known as soak testing—is a type of non-functional performance testing that evaluates how a software application behaves under a normal, steady load over an extended time. The goal isn’t to simulate sudden traffic spikes (as with stress testing) or peak loads (as with load testing), but to observe how the system handles sustained usage over several hours, days, or even weeks.

Think of endurance testing as the software equivalent of running a car engine non-stop for 48 hours on the highway—not to see if it can go fast, but to see if it can go far without overheating, leaking oil, or failing unexpectedly. Endurance testing is performed to ensure long-term reliability, resource efficiency, and system health over time.

What makes endurance testing unique is its ability to uncover time-dependent issues that don’t show up in shorter tests. These can include:

• Memory leaks that slowly consume system resources until a crash occurs
• Database connection leaks that eventually max out the pool
• Performance degradation where response times gradually increase
• Thread starvation or deadlocks that emerge under prolonged concurrency
• Unreliable scheduled tasks (e.g., cron jobs, backups, alerts) that fail intermittently
• Caching issues where stale or excessive data buildup causes side effects

Unlike other types of performance testing that measure system capacity or responsiveness under load, endurance testing is concerned with behavior over time—the patterns that emerge only after hours of normal operation. This is particularly crucial for modern systems that run continuously in production environments, such as:

• SaaS platforms used across global time zones
• Banking and fintech applications that process data 24/7
• Healthcare systems where uptime is critical
• Streaming and content delivery platforms
• IoT or real-time monitoring systems with constant data input

A successful endurance test will simulate a realistic, sustained load using scripts and data that mirror real-world user behavior. During the test, teams monitor not just performance metrics like CPU and memory usage, but also logs, error rates, and system health indicators to track anomalies that develop over time.

The true value of endurance testing lies in its ability to reveal whether your system can maintain consistent performance without deteriorating, helping you catch and fix issues before they surface in production environments.

Why endurance testing matters

Users today expect applications to be available and responsive at all times, and software must perform reliably not just during peak usage, but over extended periods, day in, day out. That's where the value of endurance testing lies.

While load testing helps verify how an application performs under a specific number of concurrent users, and stress testing identifies how it reacts under extreme conditions, endurance testing focuses on stability and consistency over time. It answers a critical question: Can your application hold up under continuous, real-world usage without degradation or failure?

Here’s why endurance testing should be a core component of your performance testing strategy:

1. It detects memory and resource leaks

Not all bugs are immediate. Some flaws emerge only after hours or days of use. A small memory leak may go unnoticed in a short test, but when compounded over time, it can exhaust available resources and crash your application. Endurance testing helps identify:

• Gradual memory consumption that increases with each user session
• Database connection leaks, where unused connections are not properly closed
• File handle or thread pool exhaustion over time

These issues are particularly dangerous in production environments where systems are expected to run nonstop and recover gracefully.

2. It uncovers long-term performance degradation

Performance doesn’t always degrade instantly. Sometimes, slowdowns creep in gradually, often due to poor cache invalidation, fragmented databases, or inefficient garbage collection. Endurance testing exposes:

• Increasing response times and latency
• Diminishing throughput
• Sluggish background processes or job queues
• Poorly managed session handling

By running the application for an extended period under a realistic workload, teams can pinpoint where and when performance starts to drop off.

3. It validates scheduled or background processes

Many systems rely on scheduled tasks—daily reports, automated backups, email campaigns, or batch jobs—that run on intervals. If these aren’t tested under real-world load over time, they can behave unpredictably. Endurance testing ensures that:

• Cron jobs and scheduled workflows function correctly without conflict
• Background services do not interfere with user-facing performance
• Long-running jobs don't lead to data corruption or locking issues

This is particularly important in systems with tight dependencies or those requiring synchronized processing.

4. It ensures stable uptime and availability

High uptime is more than a selling point—it’s often a contractual obligation backed by SLAs. Endurance testing helps teams verify that:

• The application can operate continuously without restarting services
• No performance bottlenecks emerge during sustained usage
• Failover mechanisms or redundant systems are functioning as expected

This is crucial for platforms that serve users across multiple time zones, where downtime in one region can result in revenue loss or compliance issues.

5. It builds confidence before deployment

Perhaps most importantly, endurance testing gives stakeholders the confidence to move forward. It assures product managers, QA leads, and DevOps teams that the application is not just “working”—it’s ready for long-term production use. The insights gained help teams:

• Reduce the risk of production outages
• Prevent post-release performance incidents
• Improve system scalability and architecture over time

In other words, endurance testing reduces surprises. And in software development, avoiding surprises after launch is a key measure of success.

You may be interested: The Different Types of Software Testing.

When to use endurance testing

Endurance testing is not something you run at the beginning of your QA cycle. It’s typically conducted in the later stages of performance testing, once your application has passed functional, integration, and load testing. At this point, you’ve already verified that the system behaves correctly and can handle expected traffic. Now, the focus shifts to verifying that it can stay stable and performant over time.

But how do you know when endurance testing is necessary? The answer often depends on your system’s architecture, usage patterns, and business requirements. 

Below are scenarios where endurance testing becomes particularly valuable—and often critical.

1. Applications that must run 24/7

If your application is expected to be continuously available without frequent restarts or downtime, endurance testing is essential. This includes:

• SaaS products serving users in multiple time zones
• Online marketplaces and e-commerce platforms
• Media streaming services like video or music apps
• Customer service tools that support global operations

These platforms can’t afford memory leaks, queue overflows, or resource exhaustion after 12–24 hours of steady usage. Endurance testing verifies that the application can stay healthy during extended runtime.

2. Systems with background or scheduled processes

Endurance testing is ideal for applications that rely on automated tasks, such as:

• Nightly backups and report generation
• Daily email or push notification dispatches
• Cron jobs or batch processing routines
• Periodic data synchronization with external services

These processes can interfere with application performance or create hidden bugs if not tested under realistic conditions. Endurance testing ensures they behave predictably under long-term load.

3. Applications with complex resource usage

Some systems have complex interactions between memory, threads, caches, and external services. Examples include:

• Enterprise applications with heavy data caching or session tracking
• Microservices architectures with multiple dependencies
• Real-time systems processing continuous input (e.g., IoT platforms)

For these, endurance testing is a valuable way to monitor resource utilization trends and avoid issues like CPU saturation, disk I/O bottlenecks, or garbage collection spikes.

4. After major infrastructure or architectural changes

If you’ve made significant changes to your environment or application design, endurance testing acts as a form of validation before you go live. This includes:

• Migrating to the cloud (e.g., AWS, Azure, Google Cloud)
• Moving from monolith to microservices
• Upgrading to new database versions or query engines

Changes like these can introduce new failure points or performance behaviors that only appear under long-term usage. Endurance testing helps ensure these systems operate reliably in the new configuration.

5. Before a major product release or SLA enforcement

If you’re preparing for a major release, expanding your user base, or about to sign a service-level agreement (SLA) with clients, endurance testing provides data-driven assurance that the system can meet promised performance and availability standards.

This becomes especially important when:

• Stakeholders expect ~99.9% uptime
• You’re launching in new global markets
• You’re onboarding large enterprise clients

A successful endurance test can be the final green light your team needs before deployment or scale-up.

You may be interested: How to Reduce Testing Time and Effort with Test Automation.

How to do endurance testing right

Endurance testing isn’t just about letting a script run for 48 hours and hoping for the best. To get reliable, actionable results, it requires thoughtful planning, realistic simulation, and precise monitoring. When done right, it not only validates the system’s long-term reliability but also helps teams proactively uncover and resolve performance and stability issues before they reach production.

Here’s how to approach endurance testing the right way:

1. Define realistic test goals

Start with a clear understanding of what you want to learn. Your endurance test should align with actual business and technical objectives. Are you looking to:

• Detect memory or resource leaks?
• Confirm your application’s ability to run non-stop for a week?
• Validate system health under continuous API calls?
• Ensure that nightly batch jobs won’t degrade performance?

Clearly defined goals help shape the scope of your test, identify what metrics to monitor, and determine how long the test should run.

2. Simulate real-world load over time

One of the most common mistakes in endurance testing is using synthetic or static data that doesn’t reflect actual user behavior. Instead:

• Use production-like datasets wherever possible
• Incorporate realistic user interactions, not just generic requests
• Simulate peak and off-peak activity cycles if relevant
• Include varied workflows—e.g., new user registration, file uploads, searches, payments

The goal is to mirror how the system is used over time. Tools like Loadero, JMeter, Gatling, or LoadRunner can help simulate realistic traffic patterns across distributed environments.

3. Establish a stable test environment

Your test results are only valid if the environment mirrors production conditions. That includes:

• Using production-grade infrastructure or staging environments
• Ensuring the same network, storage, and database configurations
• Avoiding tests on unstable or shared environments where external factors may skew results

Stability in the test environment ensures that any performance degradation or failure is caused by the application, not by testing variables.

4. Monitor key performance metrics continuously

Endurance testing is as much about observation as it is about execution. Set up continuous monitoring for:

• CPU, memory, disk I/O, and network usage
• Thread and connection counts
• Garbage collection behavior
• Database performance (e.g., open connections, query times)
• Error rates and exceptions in logs
• Application response times and throughput

Use tools like Prometheus, Grafana, New Relic, Datadog, or Elastic Stack (ELK) to visualize metrics in real time and detect anomalies before they escalate into failures.

5. Run the test long enough to surface issues

Endurance tests need time to reveal patterns. A test that runs for an hour may show that the system performs under load, but it won’t uncover cumulative degradation. How long you run the test depends on your context:

• 24 to 48 hours is typical for many web applications
• 5 to 7 days may be appropriate for enterprise systems or critical infrastructure
• Consider running over multiple cycles, such as daily peak usage and nightly maintenance tasks

What matters most is that the duration reflects actual use cases and provides enough time for slow-building issues to emerge.

6. Analyze trends—not just failures

Don’t wait for a crash to consider your test a failure. Instead, watch for warning signs such as:

• Gradual memory usage increase over time
• Slower response times after a certain number of hours or users
• Logs showing repeatable but non-fatal errors
• Declining throughput despite stable load

These indicators suggest that the application may fail under longer or heavier use, even if it “technically” passed the test window. Treat such trends as opportunities for optimization.

7. Document findings and optimize iteratively

Your endurance test results should feed directly into performance tuning. Create detailed reports covering:

• When anomalies occurred (timestamped)
• Which components were affected
• Resource usage trends over time
• Logs or error patterns observed
• Actions taken (e.g., memory tuning, connection pooling improvements)

Repeat the test after optimizations to validate the improvements. Endurance testing is not a one-and-done task—it’s an ongoing process as your product evolves.

The round-up: endurance testing builds long-term confidence

In software development, delivering a fast and feature-rich application is only part of the equation. Long-term reliability, stability, and performance under sustained use are what truly set high-quality software apart, especially in today’s global, always-on digital ecosystem.

Endurance testing plays a critical role in getting your system ready for launch and for the long haul. By simulating real-world usage over extended periods, it uncovers time-dependent issues like memory leaks, resource exhaustion, and performance degradation that shorter tests simply miss. Whether you’re supporting a 24/7 service, rolling out a major release, or preparing to meet strict SLAs, endurance testing gives your team the insight and confidence to move forward with fewer surprises and less risk.

At TestDevLab, we help software teams implement robust performance testing strategies—endurance testing included—that go beyond basic metrics and provide actionable insights. Our engineers work closely with clients to uncover hidden issues, optimize system behavior, and ensure products perform consistently over time.

Ready to test your system’s endurance? Get in touch with us to learn how our QA experts can help strengthen your software’s long-term performance—before your users uncover the cracks.