This week,I am revisiting some fundamental test case design techniques: equivalence partitioning and boundary value analysis. While these terms might sound complex, they offer a structured and efficient approach to software testing, particularly for numerical inputs or situations with defined input ranges.
Equivalence Partitioning: Dividing the Input Landscape Strategically
Imagine a program that validates user age for login purposes. Traditionally, one might be tempted to test every single possible age value from 0 to 120 (or whatever the defined limit may be). This brute-force approach, however, quickly becomes impractical and inefficient as the number of possible inputs grows. Equivalence partitioning offers a more strategic solution.
Equivalence partitioning involves dividing the entire set of possible input values (the input domain) into distinct classes where the program is expected to behave similarly for all values within a class. These classes are called equivalence partitions. In the age validation example, we could define the following equivalence partitions:
- Valid Ages: This partition encompasses all ages that fall within the expected range for a user (e.g., 0 to 120).
- Invalid Ages: This partition includes all values outside the valid range, such as negative numbers or values exceeding the limit (e.g., negative numbers or ages greater than 120).
- Empty or Null Values: This partition considers scenarios where the user leaves the age field blank or enters an invalid value that evaluates to null.
By identifying these partitions, we can significantly reduce the number of test cases needed for comprehensive testing. Instead of testing every single age within the valid range, we can select representative test cases from each partition. For example, we could test valid ages with values at the beginning, middle, and end of the range (e.g., 0, 30, and 120). Similarly, we could test invalid ages with a negative number and a value exceeding the limit.
Boundary Value Analysis: Sharpening Our Focus on Critical Areas
Equivalence partitioning provides a solid foundation for test case design. However, it’s important to pay close attention to the boundaries or edges of each partition. This is where boundary value analysis comes into play. Boundary value analysis focuses on testing the specific values that lie at the borders of each equivalence partition. This includes:
- Minimum and Maximum Valid Values: In the age validation example, this would involve testing the program’s behavior with values at the beginning (0) and end (120) of the valid age range.
- Values Just Above and Below the Valid Range: This involves testing one value above the maximum valid age (e.g., 121) and one value below the minimum valid age (e.g., -1).
The rationale behind testing these boundary values is that programs are often more susceptible to errors at the edges of their input domains. By testing these specific values, we can identify potential issues that might be missed by random testing within the valid range.
Conclusion
Equivalence partitioning and boundary value analysis are valuable tools for software testers. They promote efficient test case design, improve test coverage, and ultimately contribute to the development of high-quality software.
From the blog CS@Worcester – Site Title by Iman Kondakciu and used with permission of the author. All other rights reserved by the author.