Boundary Value Testing Explained

Boundary Value Testing

A Quintessential Black Box Testing

No software development can be claimed to be complete without testing the functional appropriateness of software or application. Black box testing is a fundamental testing methodology that tests the functional capabilities of the software and ensures the software meets the expectations of the client. And when it comes to black box testings, nothing can beat boundary value testing. In our blog today, we will discuss every bits and piece that you must know about boundary value testing.

What is Boundary Value Testing?

Boundary value testing is one of the most widely applied black box testing methodologies across the globe. It is defined as a black box test technique that identifies the errors and bugs between the extreme limits or boundaries of a software program or module. The extreme ends are also known as boundary values and are tested thoroughly in this process. It doesn’t require focusing on the internal coding structure, know-how of the internal paths, and implementation details. It tests the behaviour of the module at the boundary values or input levels instead of checking the errors in the centre of the module.

To perform boundary value testing, you need to set the boundary values or input variables at:

  • Minimum
  • Just above the minimum
  • Just below the minimum
  • A nominal value 
  • Just below the maximum
  • Maximum 
  • Just above the maximum

The test cases are designed to suit the testing requirements as well as fit to test the functionalities at the boundaries of the program. It is also used as a part of negative and stress testing.

Why this Testing?

This testing is imperative when it comes to testing the functional competence of software modules. The following factors justify the necessity and benefits of boundary value analysis:

  • Functionality errors are likely to be higher at the boundaries than at the core of the program.
  • It tests both valid and invalid input limits for a specific range of a software module.
  • Conducted on a limited number of test values (largely only on the boundary values) instead of using every value in the test data.
  • One of the most appropriate testing techniques used for calculation-intensive and extensive test cases with exhaustive test input variables.
  • The test cases for boundary value testing are designed based on clear guidelines and framework. Thus, eliminating any chance of compromising the boundary values and ensuring maximum testing effectiveness.

How to Do Boundary Value Testing?

Now that you have the concept cleared about boundary value testing, it is time that you learn how to perform it. Here are what you need to do to conduct boundary value analysis:

  • Create the Equivalence partitioning to test the area.
  • Focus on the valid partition and identify the boundaries in the following steps – 
    • Determine the exact boundary values.
    • Derive the boundary value that is one below the exact boundary values.
    • Derive the boundary value that is one above the boundary values.
  • Determine the valid and invalid boundary values based on the previous step.
  • Check if the testing requires amalgamating both boundary value testing and equivalence partitioning testing and determine the design of the test cases accordingly.

Pitfalls of Boundary Value Testing

While boundary value testing is a widely used black-box testing mechanism, it also has some minor drawbacks. Let’s glance at the pitfalls of boundary testing analysis listed below:

  • It is not capable of testing all the input values of a test case. But is limited only to the parameter values.
  • It is not suitable for testing the Boolean values as Boolean data has the values 0 and 1 only.
  • It is reliant on test case variables that already possess input value conditions.
  • The success of the test depends largely on the equivalence partitioning values identified for the test case.
  • It cannot be used to test programs and modules with open-ended or uni-dimensional boundaries.

Summary

After analyzing the nuances of this testing, we can safely conclude that it is one of the most preferred and recommended black box testing methodologies. It can be used for testing the parameter values of the module. It is also a great option for testing modules with large test input values in a limited time. However, this is not fit for testing those cases with one-dimensional or open-ended test cases. A simple slip in determining the equivalence partitioning values can result in absolute failure of the testing. Thus, testers must come with extensive dexterity in this area and perform the test with maximum agility and perfection.

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