Validation & Testing
Test Data Types
Always test with three types of data:
Normal Data
Typical, expected values that should work correctly.
Example: For age 0-120, test with 25, 50
Boundary Data
Values at the edges of valid ranges.
Example: For age 0-120, test with 0, 1, 119, 120
Invalid Data
Values outside acceptable range or wrong type.
Example: -5, 150, "abc", empty
Trace Tables
A systematic way to trace through code and check logic step by step.
Example: Sum numbers 1 to 3
total ← 0
FOR i ← 1 TO 3
total ← total + i
ENDFOR
OUTPUT total
| Step | i | total | Condition |
|---|---|---|---|
| 1 | - | 0 | Initial |
| 2 | 1 | 1 | 1 ≤ 3 ✓ |
| 3 | 2 | 3 | 2 ≤ 3 ✓ |
| 4 | 3 | 6 | 3 ≤ 3 ✓ |
| 5 | 4 | 6 | 4 ≤ 3 ✗ Exit |
Output: 6
Common Errors
- Syntax errors - Spelling mistakes, missing punctuation (detected by compiler)
- Logic errors - Program runs but gives wrong results (harder to find)
- Runtime errors - Program crashes during execution (divide by zero)