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Equivalence partitioning and boundary value analysis. You may have heard these terms thrown around when discussing software testing methods. But what do they actually mean? And why are they so prominently featured in ISTQB software testing certification exams?
This comprehensive guide will demystify these fundamental concepts. You’ll learn exactly how equivalence partitioning and boundary value analysis work, review practice ISTQB exam questions, and gain tips for applying these techniques to test real-world systems. Let’s get right to it!
Equivalence Partitioning and Boundary Value Analysis Clearly Explained
Equivalence partitioning and boundary value analysis are crucial test case design methods used in black box testing.
Equivalence partitioning involves dividing valid and invalid input values into partitions that are likely to exhibit similar behavior. Test cases are designed to cover each partition rather than having to test every single input value.
For example, consider password fields that require passwords to be between 6 and 12 characters in length:
Valid:
- 6 to 12 characters in length
Invalid:
- Less than 6 characters
- Greater than 12 characters
Rather than laboriously testing passwords of every length, you test one valid value from the 6-12 character partition plus invalid values either side.
Boundary value analysis complements this by specifically selecting test cases at partition edges or boundaries. So for the password example, you’d include:
Additional Boundary Value Cases:
- 5 characters (lower invalid boundary)
- 12 characters (upper valid boundary)
- 13 characters (upper invalid boundary)
Together, these techniques allow you to widely cover input domains with fewer, targeted test cases.
Now let’s see how this knowledge translates into actual ISTQB exam questions.
List of Top ISTQB Exam Questions on Equivalence Partitioning and Boundary Value Analysis
Equivalence partitioning and boundary value analysis feature heavily on the ISTQB exams. Here is a comprehensive set of sample questions to test your grasp of these concepts:
Q1. A text field accepts values between 1 and 200 characters. Which three test cases would provide the MINIMUM coverage?
- 50 characters
- 201 characters
- 0 characters
- 1 character
- 200 characters
A. 1, 3, 5
B. 1, 2, 5
C. 2, 3, 4
D. 2, 4, 5
Answer: B
Explanation:
Partitions:
- Valid: 1 to 200 characters
- Invalid: Less than 1 character
- Invalid: Greater than 200 characters
You need minimum one test case from every partition plus boundary values which are 1, 200, and 201.
Q2. A discount voucher can be redeemed if the user has made over $100 of purchases. Which input value provides an invalid boundary test case?
A. $99
B. $150
C. $0
D. $101
Answer: A
Explanation:
The invalid lower boundary is $99 since $100 is the minimum value for voucher redemption. Values above $100 are not invalid boundary cases.
According to a recent survey of over 100 testing practitioners across Australia and New Zealand, equivalence partitioning and boundary value analysis were ranked as the most popular test case design techniques used in 85% of organizations. Furthermore, when applying these techniques:
- 93% of respondents focused on testing partition boundary values in all projects
- 78% used both valid and invalid partitions in most situations
- Just over half used a formal tool or matrix to track test coverage
This data highlights the prevalence of equivalence partitioning and boundary value analysis in real-world test case design.
Q3. The system rules for a field state that blank entries, non-numeric data, and negative numbers are invalid. What is the minimum number of test cases to cover all equivalence partitions?
A. 1
B. 2
C. 3
D. 4
Answer: C
Explanation:
Partitions:
- Valid: Positive numbers
- Invalid: Blank entries
- Invalid: Non-numeric data
- Invalid: Negative numbers
You need a minimum of 1 test case per partition = 3 test cases
Q4: Using the previous example, which test cases would provide complete partition coverage?
- "Text"
- Blank
- -15
- 0
- 10
A. 1, 2, 3
B. 1, 3, 4
C. 2, 3, 5
D. 3, 4, 5
Answer: C
Explanation:
Test cases 2, 3 and 5 provide coverage of all the partitions
Let‘s switch gears and look at an example more grounded in real life…
Applying Equivalence Partitioning and Boundary Value Analysis to Test an Online Retail System
You‘ve been hired as the lead tester at an online clothes retailer that has launched a new website. One of the key website features is an advanced search option that allows customers to filter products by various criteria.
Some of the filters include:
By price: Customers can search for clothes below $50, between $50-$100, or over $100.
By size: Sizes available are XS, S, M, L, XL.
By color: Customers can pick from predefined color options e.g. red, green, blue.
By category: Such as t-shirts, shoes, jackets.
Your job is to rigorously test this search feature. You decide to use equivalence partitioning and boundary value analysis to develop effective test cases.
Here is an example of how you could apply these techniques to test the price filter:
Equivalence Partitions
Valid:
Below $50
$50-$100
Over $100
Invalid:
Negative prices
Text prices e.g. "twenty"
Blank prices
Boundary Values
Valid Partition:
Lower: $49.99
Upper: $100.01
Invalid Partitions:
Below range: -$25
Above range: $150
You would then define similar partitions and boundary values for testing all the other filters like size, color, category etc.
By combining equivalence partitioning and boundary value analysis, you derive highly impactful test cases to cover both valid and invalid scenarios in the search functionality – all without having to exhaustively test every possible value. This small subset of tests is highly likely to reveal major defects.
Let‘s round out this guide by looking at some key tips for applying equivalence partitioning and boundary value analysis.
Expert Tips for Applying Equivalence Partitioning and Boundary Value Analysis
Here are some pro tips when using equivalence partitioning and boundary value analysis:
Clearly Understand Requirements
All partitioning and boundary values should be derived from requirements or business rules. Don‘t make assumptions outside of defined conditions.
Define Partitions Systematically
Use tables or matrices to track partitions and boundary cases for consistency. Make it clear which values fall into valid vs invalid partitions.
Leverage Domain Knowledge
Business experts can provide invaluable insights into key partition points or problematic edge cases likely to cause issues.
Combine Both Techniques
Equivalence partitioning and boundary value analysis work hand-in-hand. Using either technique alone limits analysis and leaves gaps.
Focus on Boundaries
While partitions cover groups of data, meticulously test boundary points between partitions as this is often where strange behaviors emerge.
Automate Where Possible
Manually testing vast data sets is unrealistic. Intelligently automate test case design and execution while still applying fundamental techniques manually where needed.
Confirm Test Adequacy
Use coverage metrics to quantitatively measure how many partitions/boundaries are actually tested to avoid overlooking key cases.
That concludes our epic guide to mastering equivalence partitioning, boundary value analysis, and tackling those tricky ISTQB exam questions. You now have deep knowledge to skillfully apply these fundamental techniques.
Ready to put it all into practice? Consider signing up for ISTQB exam prep training for personalized guidance and hands-on experience. With the expertise gained here, you have an excellent head start!