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The Importance of Stability and Reliability Testing in Software Development

Nov 12, 2019
8 min read

There are aspects of software testing that often plant confusion in those new to the process — such as drawing the line between stability and reliability testing. The two are often used interchangeably and share a common goal of ensuring a system can perform steadily over a chosen time frame. 

In this post, we’ll take a closer look at what is stability testing, the definition of reliability testing, their objectives, and their subsets. You will find out why missing out on stability and reliability testing increases the software maintenance costs and why it is an absolute must for business managers. 

Reliability Testing Definition

The reliability test definition is an activity that determines if there are data leaks (stability testing) and how much time is needed for the system to recover after a failure (recovery testing). Beyond that, it also analyzes the behavior under peak loads and during (stress/spike testing) an emulated component failure (failover testing). The goal of reliability testing is to improve the mean time between failure (MTBF), mean time to failure (MTTF), and mean time to repair (MTTR) and offer a set of improvement guidelines for the development team. 

Software reliability is typically measured as system availability — the value shouldn’t be lower than 99%.

The Objective of Reliability Testing

The chief goal of reliability testing is to validate the performance of the product under realistic conditions. There are other goals the testing helps project teams achieve — such as the following:

  • Finding the primary driver of software failure
    Along with pinpointing the patterns system errors follow. Reliability testing helps QA teams detect the cause of failure, capture the time-to-failure metric, and measure the system’s stress levels.
  • Finding out how many failures
    Are occurring at a given time, as well as the mean life of every failure.
  • Discovering the perceptual structure of the breakdown
    Based on the result of the failure analysis, a QA tester should offer the support team a set of comprehensive guidelines that describe the corrective actions that help lower the probability of system failure occurring again.
  • Determining the speed of system recovery after a shutdown
    To find how much time the software needs to restabilize, testing teams capture the mean time to repair (MTTR), dividing the maintenance time by the number of corrective actions.
  • Improving component reliability
    To determine if the corrective actions increase the mean life of components, calculate the desired confidence levels, and devise a plan that will help maintain high system reliability.

Importance of Reliability Testing in Software Testing

Software tools are used across all domains of modern society — including the most critical ones like healthcare or security. Since a system failure can result in financial losses, halt the development of entire industries, and cause casualties, it’s crucial for IT specialists to have ways of determining if a tool is reliable enough to be adopted on a large scale. 

Here’s why project managers and company owners cannot miss out on stability and reliability testing:

  • Measures failure intensity
    Being familiar with the structure of the most widespread failures, their chief causes, and the behavior of the product prior to, during, and immediately after a shutdown improves the precision of risk mitigation and contingency planning. After completing software reliability testing, project teams will be able to forecast the increase in failure rates and prepare a set of correcting mechanisms beforehand.
  • Allows to estimate future failures
    Thanks to its broad scope, reliability testing helps software testers predict the probability of system failures on all levels of the software — unit, component, subsystem, and system.
  • Reduces the risk of system failure
    The evaluation of the efficiency of corrective actions is a technique of reliability testing. After the phase is complete, the project team will know if the chosen countermeasures are an effective way to prevent and eliminate system failures.

Types of Reliability Testing

Software reliability testing includes several subsets that analyze the system from various angles, validate the intensity of failures, the efficiency of software recovery, as well as the amount of stress the application is capable of withstanding. 

These are the most common types of reliability testing:

1. Stress testing

Stress testing refers to subjecting the system to a workload that’s beyond its original capacity. In this scenario, QA engineers reach and exceed the breaking point of the system to observe the shutdown and calculate the time needed for a full recovery. 

Here are the main stress testing activities:

  • Determining the breaking point and the save usage limit of the system;
  • Confirm there’s no data loss or a critical functional fault in the aftermath of the shutdown;
  • Determine the models of failure;
  • Create a mathematical model for breaking point prediction.

2. Recovery testing

Recovery testing implies forcing the system to fail to observe and analyze the recovery process. The objective of recovery testing is to determine how much time a given application needs to restabilize after a crash or a hardware malfunction. 

System failures are emulated during performance testing under normal estimated loads. Here are a few reliability testing example cases that fall into the domain of recovery testing:

  • Shutting down the hardware when the application is running and checking the data integrity afterward;
  • Emulating of unplugging the connecting cable when the application is undergoing a data transaction process with the network and testing the ability of the software to continue the operation when the connection is suspended;
  • Making sure that the system can recover the latest changes once restarted after an emergency shutdown or a crash.

3. Failover testing

A failover test verifies if the software is able to migrate all operations to a different server during a server failure or an outage and emulates the failures in associated systems. Ideally, development teams strive to implement automated failover meaning that the system will keep functioning properly despite the equipment, server, or network downtime. 

4. Stability testing

Stability testing is a reliability testing subset that refers to validating the absence of resource leaks and the correctness of variable deinitialization. When running stability tests, software testers emphasize error handling verification and scalability. 

The main objective of software stability testing is to determine the limitations of an application before the product’s public release. 

Stability Testing Definition

Stability testing is a range of activities designed to validate if a software product can perform with no performance defects or crashes within or beyond established time frames under high stress levels. 

Since the stability of an application can only be determined after monitoring it for an extended time frame, the testing activities include the repetitive execution of a test and comparing the outcomes with those of the initial outcome. 

The Objective of Stability Testing

Stability testing is an essential part of quality assurance as it helps frame out the limitations of the software, gives more insight into the issues the project team will have to face post-release, and pinpoints the areas that should be improved before the launch of the final build.

Here are the main objectives of completing a stability testing protocol:

  • Test the stability of the system under close to the maximum loads and ensure the system can handle high traffic and data loads.
  • Monitor the effectiveness of the system under test and increase the team’s confidence in the software’s error-free development process prior to the release.
  • Ensure that the system has no memory leaks, unprecedented shutdowns, or abnormal behaviors outside the development environment.

Importance of Stability Testing in Software Testing

A business manager can determine the stability of their software project only by examining it in an extended time frame. By putting heavy loads on the application and testing the system response, the project team is well-prepared to handle post-release issues. 

Other than that, stability testing helps identify failures and crashes that will only show over an extended period of time — it’s the only form of testing that offers such a perspective. 

As for the role of stability testing in quality assurance, here’s why this phase is an essential part of any testing cycle:

  • Provides confidence in system performance and improves forecasting precision.
  • Ensures that a system can work for extended time periods under a high load of concurrent users or stored data.
  • Reduces the odds of system downtime by pinpointing and eliminating the causes of most common and damaging system failures.
  • Detects primary system defects — incorrect object liberation from the system memory (sessions, data structure, etc.)

What Problems do Stability and Reliability Testing Solve?

Other than helping mitigate the risks of system failures and shutdowns by quickly pinpointing functionality and performance issues and ensuring the system will not degrade under high loads, stability and reliability testing solve a wide range of software maintenance issues.

  • Crashes and hangs
    Stability and reliability testing validate the performance of a system all the way to its breaking point, identifying shutdowns and responsivity issues. These tests are geared towards offering developers insights into which software components are the cause for crashes and guiding the team towards the software improvement until the product ready for a release.
  • Data loss and file corruption
    Reliability and stability testing help ensure that user data is not affected by the shutdown. In case a security vulnerability has been flagged, pinpointing the issue before release gives more time to mitigate what can be exploited and reduces the amount of pressure put on the development team.
  • Errors in programs
    The tests will examine every component of the software for errors that can’t be detected during any different test and pinpoint the failures on all levels of the software architecture.
  • Cache problems
    Stability and reliability testing helps ensure that the system performance is still proper after fine-tuning a cache.
  • Load balancing issues
    Shutdowns/turn-ons of separate server cluster nodes — determining the shutdown/turn-on delay.
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Reliability and stability test processes help testing teams model the behavior of the software with striking precision and account for irregular failures, restarts, and shutdowns. These tests increase the visibility of all system components and provide deep insights for designing correcting mechanisms. 

Project teams will have a better idea of the damage a heavy system failure can yield and the amount of time and resources needed to recover the system — no real-world scenario will catch you by surprise. 

If you want a skilled team of software testers to check the stability and reliability of your project, reach out to PFLB. Our team of software testers is skilled enough to handle both small- and large-scale projects across all industries. We will offer continuous support and assistance, collaborate with the development team, and document every test so that your tech team can use the data as a point of reference. 
Take a look at our portfolio to see how PFLB testers approach test design and execution. Leave us a message to discuss reliability and stability testing for your project.

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