What is Boundary Value Analysis?
Boundary value analysis is one of the best testing techniques in the software industry for testing software functions. It tests and detects if the software functions perfectly with the boundary values. The above technique tests values on, inside and outside particular boundaries. Testers detect major issues by analyzing the boundary conditions and ensuring the software works perfectly.
Boundary Value Analysis(BVA) comes from the understanding that programmers tend to make errors around the boundaries eg. when using equal to(=), greater than, less than, greater than-equal to, less than-equal to or the number of times a loop should be run. Boundaries are quite common in any program. For example, consider the driving license application: age of applicant should be greater than or equal to 16 for driving license. In this example, the most likely errors would be around the boundaries : ages equal to 15, 16, 17.
This idea of boundaries works well with equivalence partitioning because partitions must have boundaries. Boundary Value Analysis is based on testing at the boundaries between partitions, and can be treated as an extension to the Equivalence Partitioning(EP). Both EP and BVA work on range of numbers, values.
The rule is that we use the boundary value itself and one value(as close as you can get) on either side of the boundary. This is called ‘three-value BVA’ or the ‘full boundary value analysis’.
Eg. The boiling point of water is at 100 degrees Celsius, so the boundary values will be at 99, 100 and 101 degrees
Two-value Boundary value analysis: In this analysis, only the boundary value and the invalid value are considered. So, for the boiling point example, only 2 values 100 and 101 will be considered.
Steps to identify the test cases:
- Identify the Equivalence partitions – valid and invalid partitions. ( Please refer to the blog on Equivalence partitioning for more information).
- Identify the boundaries for each of the partitions and write test cases for the boundaries identified using BVA.
The benefits of boundary value analysis
Testers enjoy countless benefits by employing effective boundary value analysis, such as.
- Wider test coverage: Since the test focuses on boundary values, a wider test scope is achieved by exploring values at the edges of input and output ranges. With effective boundary value analysis, testers ensure critical values are systematically tested, and defects are identified.
- Better software quality: By testing the boundary conditions thoroughly, the overall quality of the software is enhanced. Since the test helps identify vulnerabilities and defects at critical points, proper software functioning is assured. The test paves the way for software to function reliably, correctly and consistently across different boundaries.
- Identification of errors early: The best part of boundary value analysis is the early identification of errors in the development life cycle. Errors are more likely to occur at the boundaries, and testers test values at the boundaries. Such errors are addressed instantly before it progresses in the system.
- Reduce risk: Boundary value analysis lessens the risk connected with boundary-related flaws. Concentrating on edge cases and critical scenarios makes the possibility of issues or failures associated with the boundary values less risky.
- More reliable: By testing boundary values, the tester verifies if the software can handle edge or extreme cases without unpredicted behavior or errors. This way, the system’s reliability is increased and authenticated according to real-world scenarios.
- Agreement with standards: Many organizations and industries mandate agreement with regulations and specific standards. By employing effective boundary value analysis, software testing is defined against the boundaries of such standards, making sure the organizations meet the agreed standards.
- Cost and time efficiency: Testers arrange testing efforts based on boundary values, and testers allocate resources also perfectly. With effective boundary value analysis, testers can reduce unwanted tests, optimize the testing process, and concentrate on a targeted approach for detecting issues.
- Customer satisfaction: By testing the boundary conditions thoroughly, the testers ensure that the software works perfectly across various outputs and inputs. Such a scenario leads to a better user experience and fewer errors as the user inputs values. Hence, overall customer satisfaction is achieved with effective boundary value analysis.
How to perform boundary value analysis
Sequences of steps are involved in effective boundary value analysis, as mentioned below.
- Finding boundaries: The first step is to understand the software’s specifications or requirements and determine boundaries as input and output values. The boundaries may possess values of any type, such as maximum or minimum values that are above or below boundaries and values accurately at boundaries.
- Partitioning input space: The next step is partitioning the input values into meaningful ranges. For example, if the values range from 1 to 100, then portioning them as values less than 1, values between 1 and 100 and values greater than 100 is necessary.
- Picking the test cases: Test cases that exercise the boundaries of every partition are picked. Concentrate on boundaries such as lower and upper, which often leads to issues. To ensure comprehensive testing always include invalid and valid test cases.
- Execution of test cases: The next step is the execution of test cases by inputting the value at boundaries and analyzing the system’s behavior. Make a note of the results of all test cases.
- Validation of expected results: Based on defined boundaries, determine the predictable results for each test case. Compare the actual and expected results to know the issues or defects.
- Document and report the issues: Document any anomalies during the test with a clear description, including the input values, actual results, expected results etc. Report the issues to the development team for further processing.
- Refine: Look at the results of boundary value analysis to see if there are any lags or areas to improve. Refine the cases and repeat the process to achieve comprehensive coverage.
Common pitfalls to avoid
While employing effective boundary value analysis, ensuring effective and accurate testing and understanding the common pitfalls is important. Look at the common pitfalls to avert while using boundary value analysis.
- Avoiding off-by-one errors: Overlooking off-by-one errors is a usual pitfall. Such errors take place during incorrect handling of boundary values.
- Insufficient partitioning: There needs to be complete coverage as input values are inadequately partitioned. Important scenarios might be noticed during testing when there are meaningful partitions of the input space.
- Avoiding invalid boundary values: Testing both valid and invalid boundary values is important and recommended. At times testers focus only on valid values averting invalid values. Hence ensuring that the system identifies and handles invalid values is important.
- Avoiding edge conditions: Edge conditions arise at the extremes of input and output values, so concentrating on these values is important. However, edge conditions trigger or expose unexpected issues.
- Overlooking boundary values combination: Though testing individual boundary values is important, testing the combination of boundary values is also essential. The interaction between various boundaries raises issues that must be identified when tested alone. It is suggested to check different combinations of boundary values to know various defects.
- Limited test data variety: By testing with a limited range of test data, there are more chances for overlooking certain issues and scenarios. Hence, including diverse values in testing by considering varied edge conditions, data types and unusual scenarios proves beneficial
Tips for effective boundary value analysis
As mentioned, there are a few tips to follow for conducting effective boundary value analysis.
1. Always understand the requirements and recognize the input and output boundaries to be tested.
2. Make meaningful partitions based on conditions or behavior.
3. Pick particular values at the boundary, which can be maximum, minimum, above or below the boundaries.
4. Test both sides of boundaries to know additional effects.
5. Focus on invalid boundary values to confirm that the system handles them appropriately.
6. Always go for a combination of boundary values as it helps to uncover potential issues.
7. Concentrate on edge conditions by testing values close to boundaries rather than exactly on them.
8. Focus on higher-risk boundaries, as failure may lead to large consequences.
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