LRUCache.test.js

import LRUCache from '../LRUCache';

describe('LRUCache', () => {
  it('should set and get values to and from the cache', () => {
    const cache = new LRUCache(100);
    expect(cache.get('key-1')).toBeUndefined();

    cache.set('key-1', 15);
    cache.set('key-2', 16);
    cache.set('key-3', 17);
    expect(cache.get('key-1')).toBe(15);
    expect(cache.get('key-2')).toBe(16);
    expect(cache.get('key-3')).toBe(17);
    expect(cache.get('key-3')).toBe(17);
    expect(cache.get('key-2')).toBe(16);
    expect(cache.get('key-1')).toBe(15);

    cache.set('key-1', 5);
    cache.set('key-2', 6);
    cache.set('key-3', 7);
    expect(cache.get('key-1')).toBe(5);
    expect(cache.get('key-2')).toBe(6);
    expect(cache.get('key-3')).toBe(7);
  });

  it('should evict least recently used items from cache with cache size of 1', () => {
    const cache = new LRUCache(1);
    expect(cache.get('key-1')).toBeUndefined();

    cache.set('key-1', 15);
    expect(cache.get('key-1')).toBe(15);

    cache.set('key-2', 16);
    expect(cache.get('key-1')).toBeUndefined();
    expect(cache.get('key-2')).toBe(16);

    cache.set('key-2', 17);
    expect(cache.get('key-2')).toBe(17);

    cache.set('key-3', 18);
    cache.set('key-4', 19);
    expect(cache.get('key-2')).toBeUndefined();
    expect(cache.get('key-3')).toBeUndefined();
    expect(cache.get('key-4')).toBe(19);
  });

  it('should evict least recently used items from cache with cache size of 2', () => {
    const cache = new LRUCache(2);
    expect(cache.get('key-21')).toBeUndefined();

    cache.set('key-21', 15);
    expect(cache.get('key-21')).toBe(15);

    cache.set('key-22', 16);
    expect(cache.get('key-21')).toBe(15);
    expect(cache.get('key-22')).toBe(16);

    cache.set('key-22', 17);
    expect(cache.get('key-22')).toBe(17);

    cache.set('key-23', 18);
    expect(cache.size).toBe(2);
    expect(cache.get('key-21')).toBeUndefined();
    expect(cache.get('key-22')).toBe(17);
    expect(cache.get('key-23')).toBe(18);

    cache.set('key-24', 19);
    expect(cache.size).toBe(2);
    expect(cache.get('key-21')).toBeUndefined();
    expect(cache.get('key-22')).toBeUndefined();
    expect(cache.get('key-23')).toBe(18);
    expect(cache.get('key-24')).toBe(19);
  });

  it('should evict least recently used items from cache with cache size of 3', () => {
    const cache = new LRUCache(3);

    cache.set('key-1', 1);
    cache.set('key-2', 2);
    cache.set('key-3', 3);
    expect(cache.get('key-1')).toBe(1);
    expect(cache.get('key-2')).toBe(2);
    expect(cache.get('key-3')).toBe(3);

    cache.set('key-3', 4);
    expect(cache.get('key-1')).toBe(1);
    expect(cache.get('key-2')).toBe(2);
    expect(cache.get('key-3')).toBe(4);

    cache.set('key-4', 5);
    expect(cache.get('key-1')).toBeUndefined();
    expect(cache.get('key-2')).toBe(2);
    expect(cache.get('key-3')).toBe(4);
    expect(cache.get('key-4')).toBe(5);
  });

  it('should promote the node while calling set() method', () => {
    const cache = new LRUCache(2);

    cache.set('2', 1);
    cache.set('1', 1);
    cache.set('2', 3);
    cache.set('4', 1);
    expect(cache.get('1')).toBeUndefined();
    expect(cache.get('2')).toBe(3);
  });

  it('should promote the recently accessed item with cache size of 3', () => {
    const cache = new LRUCache(3);

    cache.set('key-1', 1);
    cache.set('key-2', 2);
    cache.set('key-3', 3);
    expect(cache.get('key-1')).toBe(1);

    cache.set('key-4', 4);
    expect(cache.get('key-1')).toBe(1);
    expect(cache.get('key-3')).toBe(3);
    expect(cache.get('key-4')).toBe(4);
    expect(cache.get('key-2')).toBeUndefined();
  });

  it('should promote the recently accessed item with cache size of 4', () => {
    const cache = new LRUCache(4);

    cache.set('key-1', 1);
    cache.set('key-2', 2);
    cache.set('key-3', 3);
    cache.set('key-4', 4);
    expect(cache.get('key-4')).toBe(4);
    expect(cache.get('key-3')).toBe(3);
    expect(cache.get('key-2')).toBe(2);
    expect(cache.get('key-1')).toBe(1);

    cache.set('key-5', 5);
    expect(cache.get('key-1')).toBe(1);
    expect(cache.get('key-2')).toBe(2);
    expect(cache.get('key-3')).toBe(3);
    expect(cache.get('key-4')).toBeUndefined();
    expect(cache.get('key-5')).toBe(5);

    cache.set('key-6', 6);
    expect(cache.get('key-1')).toBeUndefined();
    expect(cache.get('key-2')).toBe(2);
    expect(cache.get('key-3')).toBe(3);
    expect(cache.get('key-4')).toBeUndefined();
    expect(cache.get('key-5')).toBe(5);
    expect(cache.get('key-6')).toBe(6);
  });
});