Phase 3: Test Case Design and Development
Test Case Design is where QA engineers transform requirements into executable test scenarios. The quality of your test cases directly determines the quality of your testing - poor test cases miss defects, waste time, and erode team confidence in QA. Professional test case design uses structured techniques to achieve maximum defect detection with minimum test effort.
Elements of a Professional Test Case
- Test Case ID: Unique identifier - links to RTM and bug reports (e.g., TC_LOGIN_001)
- Test Case Title: Clear description of what's being tested (e.g., 'Login with valid credentials')
- Preconditions: Conditions that must be true before execution (e.g., 'User account exists, not locked, application running')
- Test Steps: Numbered, atomic steps that any tester can follow without ambiguity
- Test Data: Specific input data to use (e.g., Username: john@test.com, Password: Test@1234)
- Expected Result: Precise, measurable outcome (e.g., 'User is redirected to dashboard, welcome message displays user's first name, session token created')
- Actual Result: Filled in during execution - what actually happened
- Pass/Fail Status: Clear binary outcome based on actual vs expected
- Priority: Critical/High/Medium/Low - used for risk-based execution ordering
Test Case Design Techniques
- Equivalence Partitioning (EP): Divide inputs into valid and invalid equivalence classes. Test one representative from each class rather than every possible value. Example: for an age field (18-65), test one value in range (35), one below (17), one above (66)
- Boundary Value Analysis (BVA): Test at and around boundaries - most defects occur at the edges. For age field 18-65: test 17, 18, 19, 64, 65, 66
- Decision Table Testing: For complex business rules with multiple conditions, create a table of all condition combinations and expected outcomes. Ensures every logical path is covered
- State Transition Testing: For features with states (e.g., order status: Pending → Processing → Shipped → Delivered → Returned), test all valid and invalid state transitions
- Exploratory Testing: Unscripted investigation where the tester uses domain knowledge and intuition to find defects that scripted tests miss. Charter: 'Explore checkout flow for 30 minutes and test payment edge cases'
Tip
Tip
Practice Phase 3 Test Case Design and Development in small, isolated examples before integrating into larger projects. Breaking concepts into small experiments builds genuine understanding faster than reading alone.
Boundary = most bugs found. Equivalence reduces test count. Decision tables for complex logic.
Practice Task
Note
Practice Task - (1) Write a working example of Phase 3 Test Case Design and Development from scratch without looking at notes. (2) Modify it to handle an edge case (empty input, null value, or error state). (3) Share your solution in the Priygop community for feedback.
Quick Quiz
Common Mistake
Warning
A common mistake with Phase 3 Test Case Design and Development is skipping edge case testing - empty inputs, null values, and unexpected data types. Always validate boundary conditions to write robust, production-ready qa engineering code.
Key Takeaways
- Test Case Design is where QA engineers transform requirements into executable test scenarios.
- Test Case ID: Unique identifier - links to RTM and bug reports (e.g., TC_LOGIN_001)
- Test Case Title: Clear description of what's being tested (e.g., 'Login with valid credentials')
- Preconditions: Conditions that must be true before execution (e.g., 'User account exists, not locked, application running')