test-case-design

# Test Case Design Techniques

## When to Use This Skill

Use this skill when:

- **Test Case Design tasks** - Working on apply systematic test case design techniques including equivalence partitioning, boundary value analysis, decision tables, and state transition testing
- **Planning or design** - Need guidance on Test Case Design approaches
- **Best practices** - Want to follow established patterns and standards

## Overview

Systematic test case design techniques ensure thorough coverage while minimizing test case count. These black-box techniques derive test cases from specifications without knowledge of internal implementation.

## Equivalence Partitioning

Divide input data into equivalent classes where any value should produce the same behavior.

### Process

1. Identify input conditions
2. Divide into valid and invalid partitions
3. Select one representative value from each partition
4. Create test cases for each partition

### Example: Age Validation (18-65)

| Partition | Range | Representative | Expected |
|-----------|-------|----------------|----------|
| Invalid (below) | < 18 | 10 | Reject |
| Valid | 18-65 | 30 | Accept |
| Invalid (above) | > 65 | 70 | Reject |

**Test Cases**:

- TC1: age = 10 → Reject (invalid below)
- TC2: age = 30 → Accept (valid)
- TC3: age = 70 → Reject (invalid above)

### Multiple Input Partitions

Combine partitions systematically:

```text
Input A: {Valid, Invalid}
Input B: {Valid, Invalid}

Combinations:
1. A-Valid, B-Valid → Expected: Success
2. A-Valid, B-Invalid → Expected: Error for B
3. A-Invalid, B-Valid → Expected: Error for A
4. A-Invalid, B-Invalid → Expected: Error for both
```

## Boundary Value Analysis

Test at and around partition boundaries where defects commonly occur.

### Process

1. Identify boundaries from equivalence partitions
2. Test at minimum, just below, just above, and maximum
3. Include special values (0, empty, null)

### Example: Age Validation (18-65)

| Boundary | Test Values | Expected |