Merge pull request #77 from luhego/add-tests-for-lru-cache

Add tests for LRUCache

Author: TheSTL

src/_Algorithms_/lru-cache/LRUCache.test.js

@@ -0,0 +1,73 @@
+const { LRUCache } = require('.');
+
+describe('Algorithms: LRU Cache', () => {
+  describe('LRUCache Instance', () => {
+    it('Should be a class', () => {
+      expect(typeof LRUCache.prototype.constructor).toEqual('function');
+    });
+  });
+
+  describe('LRUCache API', () => {
+    let lruCache = new LRUCache(4);
+
+    beforeEach(() => {
+      lruCache = new LRUCache(4);
+    });
+
+    describe('get(key)', () => {
+      it('Should return false if the LRUCache is empty', () => {
+        expect(lruCache.get('foo')).toEqual(false);
+      });
+
+      it('Should return cached value if the key exists in the LRUCache', () =>{
+        lruCache.set('foo', 'bar');
+        expect(lruCache.get('foo')).toEqual('bar');
+      });
+
+      it('Should move least recently used key to the beginning of the list', () => {
+        lruCache.set('key1', 'value1');
+        lruCache.set('key2', 'value2');
+
+        expect(lruCache.list.head.next.data['key']).toEqual('key2');
+        expect(lruCache.list.head.next.data['value']).toEqual('value2');
+
+        // The least recently used key is moved at the beginning of the list
+        lruCache.get('key1');
+        expect(lruCache.list.head.next.data['key']).toEqual('key1');
+        expect(lruCache.list.head.next.data['value']).toEqual('value1');
+      });
+    });
+
+    describe('set(key, value)', () =>{
+      it('Should append each <key:value> pair to the beginning of list', () => {
+        lruCache.set('foo', 'bar');
+        expect(lruCache.list.head.next.data['key']).toEqual('foo');
+        expect(lruCache.list.head.next.data['value']).toEqual('bar');
+      });
+
+      it('Should update value if key already exists', () => {
+        lruCache.set('foo', 'bar');
+        lruCache.set('foo', 'newBar');
+        expect(lruCache.get('foo')).toEqual('newBar');
+      });
+
+      it('Should remove node at the end if the LRUCache capacity is filled', () => {
+        lruCache.set('key5', 'value5');
+        lruCache.set('key4', 'value4');
+        lruCache.set('key3', 'value3');
+        lruCache.set('key2', 'value2');
+        lruCache.set('key1', 'value1');
+
+        expect(lruCache.list.length()).toEqual(lruCache.size);
+        expect(lruCache.list.head.next.data['key']).toEqual('key1');
+        expect(lruCache.list.head.next.data['value']).toEqual('value1');
+        expect(lruCache.list.head.next.next.data['key']).toEqual('key2');
+        expect(lruCache.list.head.next.next.data['value']).toEqual('value2');
+        expect(lruCache.list.head.next.next.next.data['key']).toEqual('key3');
+        expect(lruCache.list.head.next.next.next.data['value']).toEqual('value3');
+        expect(lruCache.list.head.next.next.next.next.data['key']).toEqual('key4');
+        expect(lruCache.list.head.next.next.next.next.data['value']).toEqual('value4');
+      });
+    });
+  });
+});

src/_Algorithms_/lru-cache/index.js

@@ -50,6 +50,7 @@ class LRUCache {
         value,
       });
       this.map.set(key, this.list.head.next);
+      return value;
     }
     return false;
   }