Soak Testing

Anushree Chatterjee

Imagine you’ve just bought a new car. Before embarking on a long road trip, you decide to test its endurance and reliability. You start by driving it continuously for several hours or even days, simulating the conditions of a long journey.

This test isn’t about speeding or testing its limits on different terrains; it’s about ensuring that the car runs smoothly over a prolonged period without overheating, breaking down, or showing signs of wear and tear that could lead to future problems.

What is soak testing?

Just as the long drive helps to ensure that the car will be reliable over long distances, soak testing helps ensure that a software application will be stable and perform well under extended periods of use.

In formal terms, soak testing, a form of non-functional testing, involves evaluating a software application under a significant load for an extended period. This test aims to discover how the system behaves under sustained use.

The application under test is subjected to real-world conditions involving heavy load and usage for durations ranging from hours to days.

Different types of performance tests

Purpose of soak testing

Through soak testing, you can bring out issues in the system while giving it a thorough test. This form of testing is mainly done to

• Identify memory leaks or performance degradation over time.
• Ensure that the software can handle expected loads over a long duration.
• Check the system’s response to continuous availability.
• Validate reliability and stability under stress.

When to opt for soak testing?

Soak testing is best suited for the following instances.

During software upgrades

• Detecting regression issues: Upgrades often involve changes or additions to the existing codebase. Soak testing can uncover any regression issues or performance degradations that these changes might introduce, especially over extended periods. Read here about the risks of late bug detection.
• Validating stability with new features: New features or changes might behave as expected under normal conditions but could lead to unforeseen issues like memory leaks or resource exhaustion over time.
• Ensuring compatibility: Ensures that the upgraded software remains compatible with existing systems and can handle long-term operational loads without failure.

During peak usage periods

• Handling high load: Applications often face their greatest challenges during peak usage times, like holiday sales for e-commerce sites. Soak testing simulates these conditions over an extended period to ensure the system can handle the load without performance degradation.
• Resource optimization: It helps identify and optimize the usage of resources under sustained heavy loads, which is critical during peak times.
• Preventing downtime: The cost of downtime during peak periods is significantly higher. Soak testing helps prevent this by ensuring the system’s endurance under stress.

For new software releases

• Baseline performance evaluation: For new versions, it is vital to understand how the system acts during prolonged use. Soak testing gives a detailed picture of the software’s performance and stability over time.
• Assurance for user experience: They usually draw in more users or lift usage levels when new versions come out. Soak testing makes sure that the satisfaction and consistency of user experience stay unchanged even with growth in continued use.
• Building trust: When soak tests are passed successfully, it gives assurance to stakeholders and users. They believe that the new release is strong and dependable for use over a long period of time.

When not to opt for soak testing?

Soak testing, while valuable for many scenarios, might not be necessary or practical in certain situations.

Short-lived applications

• Transient nature: Applications designed for short-term use, like event-based apps or temporary marketing campaigns, may not benefit from soak testing, as they are not expected to run continuously over extended periods.
• Limited usage window: The effort to conduct soak testing may not be justified if the application will only be active for a short duration.

Time and budget constraints

• Resource-intensive: Soak testing is time-consuming and requires significant resources. In projects with tight deadlines or limited budgets, prioritizing more immediate and impactful forms of testing might be more beneficial.
• Cost-benefit analysis: The cost of conducting soak testing may not always be justified, especially if the risk of long-term performance issues is low or if the application will undergo frequent changes.

Limited resources

• Hardware and personnel constraints: Soak testing requires dedicated hardware and monitoring over extended periods, which might not be feasible for teams with limited resources.
• Other testing priorities: In a resource-constrained environment, the focus might need to be given to other critical testing activities that ensure basic functionality and security.

Stable applications

• Proven track record: Applications that have been in use for a long time without any significant performance issues might not need frequent soak testing.
• Low risk of performance degradation: If an application has demonstrated consistent performance and stability over its lifecycle, especially under varied loads, the likelihood of new, undetected long-term issues emerging might be low.

Applications with frequent updates

• Rapid deployment cycles: The long duration of soak testing may not align well with the rapid deployment cycle for applications that are updated frequently.
• Continuous Integration/Continuous Deployment (CI/CD) practices: Modern development practices with quick iterations may render soak testing less practical, as each new release would theoretically require a new round of testing.

Examples of where soak testing is used

Soak testing is useful in scenarios where software applications are expected to run continuously for extended periods without failure or performance degradation. Here are some examples across fields.

• E-Commerce websites: For websites with high traffic, especially during peak shopping seasons like Black Friday or Cyber Monday, soak testing ensures that the website can handle continuous heavy traffic without crashing or slowing down, which is crucial for maintaining sales and customer satisfaction.
• Banking and financial systems: These systems often process transactions 24/7. Soak testing can help ensure the systems can handle continuous loads without errors or delays. This is vital for maintaining trust and reliability in financial transactions.
• Streaming services: Platforms like Netflix or Spotify, where users stream content continuously, soak testing can identify issues like memory leaks or buffering problems that might arise after the system has been streaming content for a prolonged period.
• Online gaming platforms: These platforms often host games that run continuously and are accessed by players around the globe. Soak testing can help ensure that the servers can handle long hours of operation without lag or downtime, providing a smooth gaming experience.
• Healthcare systems: Critical healthcare applications, like patient monitoring systems, need to operate continuously without failure. Soak testing can ensure that these systems reliably record and transmit patient data over extended periods.
• Cloud services: Services like AWS or Azure that offer continuous cloud computing services. Soak testing can help ensure these services can handle prolonged and varied workloads without service interruption.
• Telecommunications systems: These systems need to manage continuous data and voice transmission. Soak testing can help identify any potential issues that could cause service interruptions or quality degradation over time in the functioning of telecom systems.
• Enterprise Resource Planning (ERP) systems: Businesses use these systems continuously for various operations. Soak testing ensures that these systems can handle long hours of operation by multiple users without performance issues. Read here how to automate ERP testing.

Issues highlighted through soak testing

You can unearth a range of issues that might not be evident in other forms of testing, particularly those related to the performance and stability of a system over an extended period.

Some key issues often identified through soak testing include:

• Memory leaks: Perhaps the most common issue identified in soak testing. Over time, a system might gradually consume more memory than it releases, leading to exhaustion of available memory and eventual system failure or significant performance degradation.
• Resource utilization issues: This includes other system resources like file handles, CPU, or network connections. In applications that rely on databases, soak testing can reveal problems with how database connections are managed, such as connections not being released back to the pool, eventually leading to the exhaustion of available connections. Over time, these leaks can lead to resource exhaustion, causing the system to slow down or crash.
• Performance degradation: Over extended periods, some systems may exhibit gradual degradation in performance. This could be due to factors like memory bloat, inefficient garbage collection, or resource contention.
• Data corruption or loss over time: Soak testing can also expose issues where data integrity is compromised over time due to factors like race conditions, which might not be evident in shorter tests.
• System stability and reliability issues: These include random crashes or unexpected behavior of the system under prolonged stress, which might be caused by issues in the code, infrastructure, or external dependencies.
• Network issues: Network bottlenecks or degradation in network performance over time can also be highlighted, which is crucial for applications dependent on network communication.
• Software bugs and glitches: Certain bugs or glitches might only become apparent when the system has been running for a long time or when certain rare conditions are met, which are more likely to occur over extended periods.

Who does soak testing?

Soak testing is typically conducted by a combination of professionals who specialize in different aspects of software development and testing. The responsibility can vary depending on the organization’s size, structure, and the complexity of the application being tested.

You will see QA testers, automation engineers, and performance testers being the main executioners of this activity. In many organizations, soak testing is a collaborative effort involving cross-functional teams that bring together different expertise and perspectives.

Process of doing soak testing

Conducting a soak test involves several steps. Here’s a step-by-step guide for you on how to perform a soak test.

Define objectives and scope

Clearly define what you want to achieve with the soak test. Are you looking for memory leaks, performance degradation, or stability issues over time? Also determine the scope of the test, including which parts of the application to test and the performance metrics to monitor.

Understand the application and user behavior

Analyze the application to understand its architecture, dependencies, and typical usage patterns. Gather data on normal and peak load conditions to create realistic test scenarios.

Set up a testing environment

Prepare a test environment that closely mirrors the production environment. This includes hardware, software, network configurations, and any other relevant aspects. Ensure you have the necessary tools for generating load and monitoring performance.

Create a test plan

Develop a detailed test plan outlining how the soak test will be conducted. This includes the duration of the test, which could be several hours to several days, the load pattern (constant, variable, etc.), and the data collection intervals. Decide on the thresholds for acceptable performance and criteria for failure. Find a test plan template to use here.

Prepare test data and scripts

Create realistic test data and scripts that mimic user behavior. Ensure these scripts can run for extended periods without intervention. Automate the start and stop of the test, if possible, to avoid manual errors and to facilitate testing outside of working hours. Here are a few best practices and coding standards to follow when writing test scripts.

Execute the soak test

Start the test by applying the planned load to the application. Ensure the load is maintained consistently throughout the test duration as per your test plan.

Monitor and collect data

Continuously monitor the application during the test. Focus on key performance indicators like CPU usage, memory usage, response times, and throughput. Log performance data for later analysis. Automated monitoring tools can be very helpful here. Know more about test monitoring and test control.

Analyze the results

After completing the test, analyze the collected data to identify any trends, anomalies, or degradations in performance. Look for issues like memory leaks, resource exhaustion, and slower response times that developed over the course of the test.

After making necessary changes to the application, consider re-running the soak test to verify that the issues have been resolved and no new issues have been introduced.

Soak testing strategies

Here are some commonly used strategies you can use to perform soak testing.

Constant or steady-state load strategy

This approach involves applying a consistent, unchanging load to the system for an extended period. The load level is typically set to mimic average expected usage. It’s useful for identifying issues that appear over time under normal operating conditions, such as memory leaks, resource depletion, or gradual performance degradation.

Constant load helps observe how system performance metrics, like memory usage and CPU utilization, change over time under a steady usage pattern.

Stepped or incremental load strategy

In this strategy, the load is gradually increased in steps at regular intervals. Each step represents an incremental increase in user load or transaction volume. It’s designed to assess how the system handles gradually increasing workloads and to identify the point at which performance begins to degrade.

By increasing the load in steps, you can pinpoint the load level at which performance issues start to occur, helping in understanding the system’s capacity limits.

Variable load strategy

This approach involves varying the load in an unpredictable pattern, increasing and decreasing at irregular intervals. The load pattern attempts to simulate real-world user behavior more closely. It is used to see how well the system copes with sudden changes in load, which is crucial for applications expected to handle sporadic spikes in user activity.

Variable load strategy helps identify how quickly and effectively the system can adapt to changing load conditions and whether these fluctuations cause performance issues.

Challenges in soak testing

Despite how beneficial soak testing can be, it still has its own set of challenges.

• Time-consuming: Soak testing requires running the application under load for an extended period, ranging from several hours to several days or even weeks. This long duration can be a significant challenge, especially in fast-paced development environments.
• Resource intensive: It demands considerable resources, both in terms of hardware and software, to simulate real-world usage conditions. Allocating these resources for prolonged periods can be costly and may impact other projects or operations.
• Complex setup and monitoring: Setting up a soak test to accurately mimic real-world usage can be complex. Continuous monitoring and logging of performance metrics over the test duration add to the complexity.
• Analyzing large volumes of data: Soak tests generate large volumes of performance data that need to be analyzed to identify issues. Sifting through this data to find meaningful insights can be time-consuming and requires specialized skills. Issues that arise during soak testing, such as memory leaks or performance degradation, can be subtle and gradual. Pinpointing the exact cause of these issues can be challenging and often requires in-depth analysis.
• Maintaining a stable test environment: Ensuring the test environment remains stable and consistent throughout the testing period can be difficult, especially for tests that run for several days.
• Keeping the test environment up-to-date: Ensuring that the test environment accurately reflects the production environment is crucial for meaningful test results but can be challenging to maintain, especially with frequent updates to the production system.

Best practices

Here are some tips that might help you effectively do a soak test.

Define clear objectives

Clearly define what you want to achieve with the soak test. Common objectives include identifying memory leaks, performance degradation, and stability issues over extended periods.

Simulate realistic load and usage patterns

Design test scenarios that accurately reflect real-world usage. This includes understanding typical user behavior, peak and off-peak usage patterns, and transaction types.

Choose an appropriate duration

Determine the test duration based on the application’s nature and usage. For instance, a system used continuously would require a longer soak test compared to one used intermittently.

Use a representative test environment

Ensure that the testing environment closely resembles the production environment in terms of hardware, software, network configurations, and data volume.

Monitor Key Performance Indicators (KPIs)

Continuously monitor and record relevant KPIs such as CPU usage, memory usage, response times, and throughput.

Automate where possible

Automate the test execution and monitoring processes. This reduces manual effort, increases repeatability, and allows testing outside normal working hours.

Regularly review and analyze results

Conduct periodic analysis during the test to identify any emerging issues. Post-test, perform a thorough analysis to understand the root causes of any problems.

Be prepared to adjust test parameters

If initial tests reveal issues quickly, be prepared to adjust the test parameters, such as reducing the load or duration, to isolate and analyze specific issues.

Ensure efficient resource allocation

Given that soak tests can be resource-intensive, plan and allocate resources efficiently to avoid disrupting other projects or operations.

Incorporate findings into development

Use insights from soak testing to improve the software. Address identified issues and consider the test results in future development and testing cycles.

Repeat tests after significant changes

Conduct soak tests after major changes to the application or environment to ensure ongoing stability and performance.

Final thoughts

Soak testing is crucial for applications requiring high reliability and uptime. It helps identify potential issues that could cause system failures or performance bottlenecks in a real-world scenario, thereby enhancing the software’s stability and performance over time.

Use suitable tools and processes to make soak testing a part of your QA process, and you will have a highly competent product in the market.

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