7a664ca3e8
Merging this separately so the commit with the tooling change is readable. This is a follow-on to #1167 which turned prettier on.
140 lines
3.7 KiB
JavaScript
140 lines
3.7 KiB
JavaScript
'use strict'
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const { expect } = require('chai')
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const LRU = require('./lru-cache')
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function expectCacheSlots(cache, keys) {
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expect(cache.cache.size).to.equal(keys.length)
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const slots = keys.map(k => cache.cache.get(k))
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const first = slots[0]
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const last = slots.slice(-1)[0]
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expect(cache.oldest).to.equal(first)
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expect(cache.newest).to.equal(last)
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expect(first.older).to.be.null
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expect(last.newer).to.be.null
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for (let i = 0; i + 1 < slots.length; ++i) {
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const current = slots[i]
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const next = slots[i + 1]
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expect(current.newer).to.equal(next)
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expect(next.older).to.equal(current)
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}
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}
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describe('The LRU cache', function() {
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it('should support being called without new', function() {
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const cache = LRU(1)
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expect(cache).to.be.an.instanceof(LRU)
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})
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it('should support a zero capacity', function() {
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const cache = new LRU(0)
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cache.set('key', 'value')
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expect(cache.cache.size).to.equal(0)
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})
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it('should support a one capacity', function() {
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const cache = new LRU(1)
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cache.set('key1', 'value1')
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expectCacheSlots(cache, ['key1'])
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cache.set('key2', 'value2')
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expectCacheSlots(cache, ['key2'])
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expect(cache.get('key1')).to.be.undefined
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expect(cache.get('key2')).to.equal('value2')
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})
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it('should remove the oldest element when reaching capacity', function() {
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const cache = new LRU(2)
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cache.set('key1', 'value1')
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cache.set('key2', 'value2')
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cache.set('key3', 'value3')
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cache.cache.get('key1')
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expectCacheSlots(cache, ['key2', 'key3'])
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expect(cache.cache.get('key1')).to.be.undefined
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expect(cache.get('key1')).to.be.undefined
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expect(cache.get('key2')).to.equal('value2')
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expect(cache.get('key3')).to.equal('value3')
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})
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it('should make sure that resetting a key in cache makes it newest', function() {
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const cache = new LRU(2)
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cache.set('key', 'value')
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cache.set('key2', 'value2')
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expectCacheSlots(cache, ['key', 'key2'])
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cache.set('key', 'value')
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expectCacheSlots(cache, ['key2', 'key'])
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})
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describe('getting a key in the cache', function() {
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context('when the requested key is oldest', function() {
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it('should leave the keys in the expected order', function() {
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const cache = new LRU(2)
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cache.set('key1', 'value1')
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cache.set('key2', 'value2')
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expectCacheSlots(cache, ['key1', 'key2'])
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expect(cache.get('key1')).to.equal('value1')
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expectCacheSlots(cache, ['key2', 'key1'])
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})
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})
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context('when the requested key is newest', function() {
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it('should leave the keys in the expected order', function() {
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const cache = new LRU(2)
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cache.set('key1', 'value1')
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cache.set('key2', 'value2')
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expect(cache.get('key2')).to.equal('value2')
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expectCacheSlots(cache, ['key1', 'key2'])
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})
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})
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context('when the requested key is in the middle', function() {
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it('should leave the keys in the expected order', function() {
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const cache = new LRU(3)
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cache.set('key1', 'value1')
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cache.set('key2', 'value2')
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cache.set('key3', 'value3')
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expectCacheSlots(cache, ['key1', 'key2', 'key3'])
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expect(cache.get('key2')).to.equal('value2')
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expectCacheSlots(cache, ['key1', 'key3', 'key2'])
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})
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})
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})
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it('should clear', function() {
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// Set up.
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const cache = new LRU(2)
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cache.set('key1', 'value1')
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cache.set('key2', 'value2')
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// Confidence check.
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expect(cache.get('key1')).to.equal('value1')
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expect(cache.get('key2')).to.equal('value2')
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// Run.
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cache.clear()
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// Test.
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expect(cache.get('key1')).to.be.undefined
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expect(cache.get('key2')).to.be.undefined
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expect(cache.cache.size).to.equal(0)
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})
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})
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