Test Case Design Techniques
Test case design techniques help testers create effective, efficient, and high-quality test cases. These techniques reduce redundancy, improve coverage, and uncover edge cases that are otherwise missed.
Strong test case design is the foundation of reliable automation.
What is a Test Case?
A test case is a set of conditions and steps used to verify that a system behaves as expected.
A test case answers:
HOW should the scenario be tested?
Test Case vs Test Scenario (Quick Recap)
- Scenario → WHAT to test
- Test Case → HOW to test
Example:
- Scenario: Verify login functionality
- Test Case: Login with valid username and password
Test Case Template (Standard)
A good test case usually contains:
- Test Case ID
- Test Scenario
- Preconditions
- Test Steps
- Test Data
- Expected Result
- Actual Result
- Status (Pass/Fail)
Characteristics of a Good Test Case
✔ Clear and unambiguous
✔ Independent
✔ Reusable
✔ Traceable to requirement
✔ Covers positive and negative paths
1️⃣ Equivalence Partitioning (EP)
What is EP?
Equivalence Partitioning divides input data into valid and invalid groups.
Idea:
Test one value from each group instead of all values.
Example:
- Age allowed: 18–60
- Valid: 25
- Invalid: 10, 70
Why EP Matters
- Reduces number of test cases
- Improves coverage
- Saves time
2️⃣ Boundary Value Analysis (BVA)
What is BVA?
Boundary Value Analysis focuses on edge values.
Rule:
Bugs often occur at boundaries.
Example:
- Range: 1–100
- Test: 0, 1, 2, 99, 100, 101
EP vs BVA
| Aspect | EP | BVA |
|---|---|---|
| Focus | Data groups | Boundary values |
| Goal | Reduce test cases | Catch edge bugs |
3️⃣ Decision Table Testing
What is Decision Table Testing?
Used when multiple conditions lead to different outcomes.
Example:
- Login allowed only if:
- Valid username
- Valid password
- Account active
Decision table maps:
- Conditions
- Actions
Best used for business rules.
4️⃣ State Transition Testing
What is State Transition Testing?
Used when system behavior depends on previous state.
Example states:
- New
- Active
- Locked
- Disabled
Transitions:
- Failed login → Locked
- Admin unlock → Active
When to Use Which Technique
| Situation | Technique |
|---|---|
| Input ranges | EP + BVA |
| Business rules | Decision Table |
| State-dependent behavior | State Transition |
Common Test Design Mistakes ❌
- Writing redundant test cases
- Missing boundary conditions
- Ignoring negative scenarios
- Over-testing low-risk areas
Interview-Ready Questions
Q: Why are test design techniques important?
A: They ensure coverage with fewer test cases.
Q: Which technique is best for boundary issues?
A: Boundary Value Analysis.
Key Takeaways
- Test design techniques improve quality
- EP and BVA reduce redundancy
- Decision tables handle complex logic
- State transitions test behavior over time
- Strong test cases lead to stable automation