The Ins and Outs of Pairwise Testing

Mar 22, 2024 | Product Insights, Test Automation Insights

Software testing typically involves taking user requirements and stories to create test cases that provide a desired level of coverage. Many of these tests contain a certain level of redundancy. Traditional testing methods can lead to a lot of wasted time and extend the deployment period. Because of that, project teams often cut down on the scope of coverage, which adds risk. Any defects found in production as a result can lead to unanticipated expenses. 

Pairwise testing increases the ability of testing teams to achieve high-quality results that increase end-user satisfaction. This article explores how it works, its impacts on quality insurance, and best practices for working pairwise testing into your review process.  

🤔 What Is Pairwise Testing?

Pairwise testing, or all-pairs testing, is a software testing design technique focused on covering all possible combinations of various input parameters from a minimal number of use cases. The goal of pairwise testing is to identify defects caused by the inputs. Focusing on pairwise combinations reduces the number of test cases required, which provides relief to testing budgets.     

Pairwise Testing Example

Let’s say you have people from different countries who want to sign up for a new social media app. Some of the fields on the input form might include:

  • Country of origin (USA, UK, Canada) (3 inputs)
  • Language (English, Spanish, French) (3 inputs)
  • Age group (18-30, 31-50, 51+) (3 inputs)
  • Subscription type (Basic, Premium) (2 inputs)
  • Payment method (Credit card, PayPal) (2 inputs)

Testing the above combinations would require us to cover all the inputs, which comes out to:

3 * 3 * 3 * 2 * 2 = 108

How long would a testing team working at full speed take to cover 108 different scenarios? Pairwise testing helps us reduce this number while accounting for all input value pairs. Let’s say you have a combination of two parameters that produce the most bugs. Finding those errors requires us to break the parameters into unique pairs for testing. Here’s how we would do that with our example:

  • Country: USA, Language: English, Age Group: 18-30, Subscription Type: Basic, Payment Method: Credit Card
  • Country: USA, Language: French, Age Group: 31-50, Subscription Type: Premium, Payment Method: PayPal
  • Country: USA, Language: Spanish, Age Group: 51+, Subscription Type: Premium, Payment Method: Credit Card
  • Country: USA, Language: French, Age Group: 18-30, Subscription Type: Basic, Payment Method: PayPal
  • Country: Canada, Language: Spanish, Age Group: 18-30, Subscription Type: Basic, Payment Method: PayPal
  • Country: Canada, Language: English, Age Group: 31-50, Subscription Type: Premium, Payment Method: PayPal
  • Country: Canada, Language: French, Age Group: 50+, Subscription Type: Basic, Payment Method: PayPal
  • Country: Canada, Language: English, Age Group: 31-50, Subscription Type: Premium, Payment Method: Credit Card
  • Country: UK, Language: English, Age Group: 18-30, Subscription Type: Premium, Payment Method: Credit Card
  • Country: UK, Language: Spanish, Age Group: 31-50, Subscription Type: Basic, Payment Method: PayPal
  • Country: UK, Language: French, Age Group: 50+, Subscription Type: Premium, Payment Method: Credit Card
  • Country: UK, Language: Spanish, Age Group: 50+, Subscription Type: Premium, Payment Method: PayPal

With the above, we’ve covered the available values from all input fields. You have:

  • All countries paired with every language
  • All countries paired with every age group
  • All countries paired with every subscription type
  • All countries paired with every payment method
  • All languages paired with every subscription type
  • All languages paired with every age group
  • All languages paired with every country

It’s much less work for a testing team to go through 12 testing scenarios versus 108. Pairwise testing allows them to provide software projects with enough testing coverage of interactions between input parameters.

💬 What Is the Purpose of Pairwise Testing in Software Quality Assurance?

As illustrated previously, pairwise testing lessens the amount of manual testing required by dealing with the exponential growth in test cases that occurs as input parameters or factors increase. You can have numerous inputs in a complex software system, making it nearly impossible to cover every scenario. 

The pairwise testing technique ensures that each pair of input parameters gets tested together at least once. That’s based on the assumption that most errors occur between two input factors versus more complex patterns. This type of dynamic testing helps test teams uncover a significant number of defects, which increases software reliability and functionality. 

📖 How to Implement Pairwise Testing Strategies

Now that we better understand how pairwise testing works, let’s look at ways you can implement the testing strategy effectively. 

Identify the Input Parameters

Start by looking for the input parameters or factors that influence your software’s behavior, which can include:

  • Configuration settings
  • Environmental variables
  • User inputs

It’s hard to set up efficient pairwise testing without understanding the above. The first step involves reviewing requirements documentation to identify critical functionalities and features needed to support the software. Next, talk to stakeholders like developers, product managers, and quality assurance professionals to gain insight into the software’s behavior. 

From there, start exploring and experimenting with how the software functions. That will give you a better sense of how different inputs affect the platform’s behavior. A hands-on approach helps discover hidden parameters that may not have been captured in requirements or disclosed by stakeholders. 

Document the parameters along with all possible options. That should serve as the basis for your pairwise testing. Tracking parameters, especially if requirements change, avoids confusion down the line and helps you keep track of your pairwise combos. 

Define the Values for Each Input Parameter

After identifying your parameters, specify the potential values or options. Those values should represent different states or conditions the software might encounter while operating. You’ll need a good deal of specificity to create meaningful test cases. 

Be exhaustive when covering all input options. Look for boundary values and edge cases. These typically represent points where defects are likely to occur. Make sure you include values right at the edge of acceptable ranges or limits for each parameter.

Think about what might happen if there is an invalid input. Testing should cover how the software handles unexpected or incorrect inputs. If a field is defined as a number, what would happen if a user entered a character? Include values that should trigger an exception message if entered. 

Create a Pairwise Test Matrix

Your pairwise test matrix is an essential comprehensive reference outlining your input parameter combinations and the values to cover in your tests. Every parameter should include a list of all possible values. Next, use a pairwise testing tool like Ranorex DesignWise to generate your pairwise test matrix.  

Once that’s done, document the expected outcomes from each test case. Your pairwise test matrix will also act as a guide for executing your test cases. Make sure you test software using each combination outlined in the matrix. 

Select a Pairwise Testing Strategy

Before going with a specific pairwise testing strategy, look at your requirements and analyze the scope and complexity of the project. Think about the critical functions and features that require testing. Next, identify all input parameters, then assess their effects on your software. 

If you have a small number of parameters, you may want to consider doing manual testing to execute your combinations. If you have a lot of parameter sets, you can benefit from the type of automated testing provided by Ranorex Studio. 

Examples of common pairwise testing strategies include:

  • Manual pairwise testing — Best for when you have a small number of input parameters or have limited comprehensive testing time and resources
  • Automated pairwise testing tools — Consider this process for projects with a moderate number of input parameters, like a few dozen, to generate your test cases.
  • Advanced pairwise testing — If you have a large number of inputs or complicated interactions, think about using more advanced methods like mathematical modeling or customized algorithms. 

Base your testing strategy on the goals you wish to achieve. Are you looking to assess the security of a piece of software, how it performs, the level of functionality, or all of the above? Let your testing goals guide you toward the best pairwise testing strategy. You can also use a tool like DesignWise for both automated pairwise testing and advanced pairwise testing because it handles small to high-complexity projects

Other considerations include:

  • Testing budget
  • Exiting tools and frameworks available
  • Dependencies and constraints

Generate Your Test Cases

Implement the pairwise testing strategy you choose into your functional testing process. Make sure you generate all possible combinations. 

  • Establish a test template — Create a standard template for your test cases. Include all input parameter values, expected results, test conditions, and other notes. 
  • Populate test cases — Use the values from your pairwise combos to populate your test cases. 
  • Consider all outcomes — Specify all expected outcomes for every test case. Include details on how the software should behave when exposed to a specific input combination. 
  • Document test conditions — Keep track of any conditions or prerequisites to put in place to execute every test correctly. 

Execute Your Test Cases

After preparing your test cases, execute them within your n-wise testing framework. Record all results during the executing phase, including any defects and issues encountered. Replicate real-world operational conditions for your software within the test environment. Manage your test data to ensure each test case receives the correct input values. 

Finally, report defects that arise during execution to the development team. Include detailed information about defects, including what input parameters acted as the trigger so the developers understand how to address them. You should also maintain test execution logs that record the outcomes of your executed tests. They are valuable for traceability, debugging, and regression testing. 

Analyze the Results

Once you execute your test cases, look at the results for any inconsistencies, defects, or unexpected behavior. Below are some tips on analyzing test results. 

  • Set up defect classification — Categorize your defects based on their severity and level of impact on software functionality. Examples of classifications include minor, major, critical, or cosmetic. 
  • Perform root cause analysis — This will help you understand better how a defect occurred. Did it occur because of a specific input combination, a dependency, or other factors? Understanding a defect’s root cause helps prevent similar future results. 
  • Initiate regression testing — Conduct regression testing to make sure that repairs made to fix a defect do not introduce new issues. 
  • Test metrics — Look at metrics like test coverage, defect density, and trend analysis. 

✅ Benefits of Implementing Pairwise Testing

Using pairwise testing on Java software or other development projects enhances the software build process and your quality assurance efforts. Below are some other advantages offered by investing in pairwise testing. 

  • More efficient test coverage 
  • Earlier defect detection
  • Improved test maintainability
  • Better test documentation
  • More effective resource allocation
  • Enhanced risk mitigation
  • Lower testing costs

📌 Tips for Implementing Pairwise Testing Strategies

A thorough understanding of the software requirements helps you define input parameters and related values more clearly for exhaustive testing. Not all input parameters are created equal, so prioritize them based on how they impact software behavior and the input’s potential to introduce defects. 

Use a Pairwise Testing Tool to Generate Test Cases

Select a pairwise testing suite that lets you perform cross-browser testing to ensure that inputs behave the same regardless of where the software operates. Ranorex DesignWise is a perfect choice preferred by many testing professionals for their software testing needs.  

Test the Most Important Input Parameters

Focus on the parameters you identified during the review process as the most critical. For example, your priority might be evaluating essential parameters in the software’s core functionality. You would start with those that impact revenue, the user experience, or align with regulatory compliance requirements.

Prioritize Test Cases That Are Likely to Reveal Defects

Look at the input parameters most likely to generate a defect. Those requiring user input through a UI might rank higher than those put in place by a backend automated process. You should also look at how frequently users might interact with various inputs, as those will have a bigger impact if they fail. It’s also a good idea to prioritize parameters with a history of defects or failures. 

🚀 Improve Your Ranorex Test Process With Pairwise Testing

Ranorex DesignWise can be used in conjunction with pairwise testing tools or strategies with the following steps:

  • Get a Pairwise Tool — DesignWise is perfect for generating pairwise combinations that you can use for your test cases.
  • Define Input Parameters — Identify all the input parameters for your application that you want to test pairwise. This could be anything from dropdown selections to checkboxes to input fields.
  • Generate Test Combinations — Use your chosen pairwise testing tool to generate combinations of inputs.
  • Integrate with Ranorex — For each combination, manually create a test in Ranorex that provides the inputs and checks the expected results. Or, take a data-driven approach and use the test combinations as a data source in Ranorex and run a single test multiple times with different data each time.
  • Execute Tests — Run your Ranorex tests as you would normally. The advantage here is that you’re now testing many possible combinations of inputs without having to manually define each one.
  • Analyze Results — With pairwise testing, you’re hoping to catch any defects caused by specific pairs of inputs interacting with each other. Review any failed tests to determine if they highlight actual defects in the software.

Remember, while pairwise testing can be very effective, it doesn’t guarantee that all defects will be caught. It’s just one strategy among many, and it works best when used in conjunction with other testing methodologies. Here is an article that explains the benefits of pairwise testing with DesignWise in more depth.



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