test-design-techniques

Test Design Techniques

<default_to_action> When designing test cases systematically:

1. APPLY Boundary Value Analysis (test at min, max, edges)
2. USE Equivalence Partitioning (one test per partition)
3. CREATE Decision Tables (for complex business rules)
4. MODEL State Transitions (for stateful behavior)
5. REDUCE with Pairwise Testing (for combinations)

Quick Design Selection:

• Numeric ranges → BVA + EP
• Multiple conditions → Decision Tables
• Workflows → State Transition
• Many parameters → Pairwise Testing

Critical Success Factors:

• Systematic design finds more bugs with fewer tests
• Random testing is inefficient
• 40+ years of research backs these techniques </default_to_action>

Quick Reference Card

When to Use

• Designing new test suites
• Optimizing existing tests
• Complex business rules
• Reducing test redundancy

Technique Selection Guide

Scenario	Technique
Numeric input ranges	BVA + EP
Multiple conditions	Decision Tables
Stateful workflows	State Transition
Many parameter combinations	Pairwise
All combinations critical	Full Factorial

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Boundary Value Analysis (BVA)

Principle: Bugs cluster at boundaries.

Test at boundaries:

• Minimum valid value
• Just below minimum (invalid)
• Just above minimum (valid)
• Maximum valid value
• Just above maximum (invalid)

// Age field: 18-120 valid
const boundaryTests = [
  { input: 17, expected: 'invalid' },  // Below min
  { input: 18, expected: 'valid' },    // Min boundary
  { input: 19, expected: 'valid' },    // Above min
  { input: 119, expected: 'valid' },   // Below max
  { input: 120, expected: 'valid' },   // Max boundary
  { input: 121, expected: 'invalid' }  // Above max
];

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Equivalence Partitioning (EP)

Principle: One test per equivalent class.

// Discount rules:
// 1-10:  No discount
// 11-100: 10% discount
// 101+:   20% discount

const partitionTests = [
  { quantity: -1, expected: 'invalid' },  // Invalid partition
  { quantity: 5, expected: 0 },           // Partition 1: 1-10
  { quantity: 50, expected: 0.10 },       // Partition 2: 11-100
  { quantity: 200, expected: 0.20 }       // Partition 3: 101+
];

// 4 tests cover all behavior (vs 200+ if testing every value)