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Testing KnapsackItem Class Implementation in javascript-algorithms

This test suite validates the KnapsackItem class implementation, focusing on item creation, value/weight calculations, and quantity management. The tests ensure proper functionality of a core component used in solving the classic knapsack optimization problem.

Test Coverage Overview

The test suite provides comprehensive coverage of the KnapsackItem class functionality.

Core property validation for value, weight, and quantity
Calculation verification of valuePerWeightRatio
Dynamic total value and weight computations
String representation testing
Edge case handling with zero quantity

Implementation Analysis

The testing approach employs Jest’s describe/it pattern for structured test organization. The implementation validates object state changes through multiple quantity modifications, ensuring proper recalculation of derived properties.

Key patterns include:

Object instantiation testing
Property accessor validation
Derived value calculations
State mutation verification

Technical Details

Testing Framework: Jest

Assertion methods: expect().toBe()
Test structure: describe/it blocks
Object-oriented testing patterns
Isolated test case design

Best Practices Demonstrated

The test suite exemplifies several testing best practices for JavaScript algorithms.

Single responsibility principle in test cases
Clear test case descriptions
Comprehensive state validation
Multiple assertion points for thorough verification
Proper setup and verification of object mutations

trekhleb/javascript-algorithms

src/algorithms/sets/knapsack-problem/__test__/KnapsackItem.test.js

            
import KnapsackItem from '../KnapsackItem';

describe('KnapsackItem', () => {
  it('should create knapsack item and count its total weight and value', () => {
    const knapsackItem = new KnapsackItem({ value: 3, weight: 2 });

    expect(knapsackItem.value).toBe(3);
    expect(knapsackItem.weight).toBe(2);
    expect(knapsackItem.quantity).toBe(1);
    expect(knapsackItem.valuePerWeightRatio).toBe(1.5);
    expect(knapsackItem.toString()).toBe('v3 w2 x 1');
    expect(knapsackItem.totalValue).toBe(3);
    expect(knapsackItem.totalWeight).toBe(2);

    knapsackItem.quantity = 0;

    expect(knapsackItem.value).toBe(3);
    expect(knapsackItem.weight).toBe(2);
    expect(knapsackItem.quantity).toBe(0);
    expect(knapsackItem.valuePerWeightRatio).toBe(1.5);
    expect(knapsackItem.toString()).toBe('v3 w2 x 0');
    expect(knapsackItem.totalValue).toBe(0);
    expect(knapsackItem.totalWeight).toBe(0);

    knapsackItem.quantity = 2;

    expect(knapsackItem.value).toBe(3);
    expect(knapsackItem.weight).toBe(2);
    expect(knapsackItem.quantity).toBe(2);
    expect(knapsackItem.valuePerWeightRatio).toBe(1.5);
    expect(knapsackItem.toString()).toBe('v3 w2 x 2');
    expect(knapsackItem.totalValue).toBe(6);
    expect(knapsackItem.totalWeight).toBe(4);
  });
});