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Test Case Design Techniques

Test Case Design Techniques are structured methods used to identify, design, and optimize test cases so that maximum test coverage is achieved with minimum effort.

These techniques answer: “What are the right test cases to test this feature?”

1. Definition

Test Case Design Techniques are structured methods used to identify, design, and optimize test cases so that maximum test coverage is achieved with minimum effort.

These techniques answer: “What are the right test cases to test this feature?”

2. Purpose of Test Case Design Techniques

  • Improve test coverage
  • Reduce redundant test cases
  • Identify edge cases
  • Design effective and efficient tests
  • Ensure systematic testing

3. Why Test Case Design Techniques Matter

  • Exhaustive testing is impossible
  • Random testing misses defects
  • Structured techniques reduce risk
  • Essential for interviews and real projects

4. Types of Test Case Design Techniques (Manual Focus)

4.1 Black Box Techniques

(Tester does not know internal code)

  • Equivalence Partitioning
  • Boundary Value Analysis (BVA)
  • Decision Table Testing
  • State Transition Testing
  • Use Case Testing
  • Error Guessing

4.2 White Box Techniques (Conceptual Awareness)

  • Statement coverage
  • Branch coverage

(Conceptual knowledge only for manual testers.)

4.3 Experience-Based Techniques

  • Exploratory Testing
  • Ad-hoc Testing
  • Error Guessing

5. When to Use Test Case Design Techniques

  • While writing test cases
  • During requirement analysis
  • When reducing large test suites
  • When testing complex business logic

6. Real-Time Example

Login field test case design:

  • Equivalence Partitioning → valid / invalid credentials
  • BVA → min/max password length
  • Error Guessing → special characters, SQL input

7. Common Mistakes

  • Writing too many similar test cases
  • Ignoring boundary values
  • Not applying techniques systematically

8. Interview-Ready Answers

Short answer:

Test case design techniques are methods used to create effective test cases with maximum coverage and minimal redundancy.

Detailed answer:

These techniques help testers identify valid, invalid, and edge scenarios systematically, ensuring thorough and efficient testing.

9. Key Takeaway

Good test case design is about smart coverage, not more test cases.