Extract Cache class from AjaxCache

app/assets/javascripts/lib/utils/ajax_cache.js

-class AjaxCache {
+import Cache from './cache';
+
+class AjaxCache extends Cache {
   constructor() {
-    this.internalStorage = { };
+    super();
     this.pendingRequests = { };
   }
-  get(endpoint) {
-    return this.internalStorage[endpoint];
-  }
-
-  hasData(endpoint) {
-    return Object.prototype.hasOwnProperty.call(this.internalStorage, endpoint);
-  }
-
-  remove(endpoint) {
-    delete this.internalStorage[endpoint];
-  }
-
   retrieve(endpoint) {
     if (this.hasData(endpoint)) {
       return Promise.resolve(this.get(endpoint));

app/assets/javascripts/lib/utils/cache.js

+class Cache {
+  constructor() {
+    this.internalStorage = { };
+  }
+
+  get(key) {
+    return this.internalStorage[key];
+  }
+
+  hasData(key) {
+    return Object.prototype.hasOwnProperty.call(this.internalStorage, key);
+  }
+
+  remove(key) {
+    delete this.internalStorage[key];
+  }
+}
+
+export default Cache;

spec/javascripts/lib/utils/cache_spec.js

+import Cache from '~/lib/utils/cache';
+
+describe('Cache', () => {
+  const dummyKey = 'just some key';
+  const dummyValue = 'more than a value';
+  let cache;
+
+  beforeEach(() => {
+    cache = new Cache();
+  });
+
+  describe('get', () => {
+    it('return cached data', () => {
+      cache.internalStorage[dummyKey] = dummyValue;
+
+      expect(cache.get(dummyKey)).toBe(dummyValue);
+    });
+
+    it('returns undefined for missing data', () => {
+      expect(cache.internalStorage[dummyKey]).toBe(undefined);
+      expect(cache.get(dummyKey)).toBe(undefined);
+    });
+  });
+
+  describe('hasData', () => {
+    it('return true for cached data', () => {
+      cache.internalStorage[dummyKey] = dummyValue;
+
+      expect(cache.hasData(dummyKey)).toBe(true);
+    });
+
+    it('returns false for missing data', () => {
+      expect(cache.internalStorage[dummyKey]).toBe(undefined);
+      expect(cache.hasData(dummyKey)).toBe(false);
+    });
+  });
+
+  describe('remove', () => {
+    it('removes data from cache', () => {
+      cache.internalStorage[dummyKey] = dummyValue;
+
+      cache.remove(dummyKey);
+
+      expect(cache.internalStorage[dummyKey]).toBe(undefined);
+    });
+
+    it('does nothing for missing data', () => {
+      expect(cache.internalStorage[dummyKey]).toBe(undefined);
+
+      cache.remove(dummyKey);
+
+      expect(cache.internalStorage[dummyKey]).toBe(undefined);
+    });
+
+    it('does not remove wrong data', () => {
+      cache.internalStorage[dummyKey] = dummyValue;
+      cache.internalStorage[dummyKey + dummyKey] = dummyValue + dummyValue;
+
+      cache.remove(dummyKey);
+
+      expect(cache.internalStorage[dummyKey]).toBe(undefined);
+      expect(cache.internalStorage[dummyKey + dummyKey]).toBe(dummyValue + dummyValue);
+    });
+  });
+});