             }
         }
         
-        let sut = MemoryCacheMock()
+        let sut = MemoryCacheMock("test")
         sut.expectation = expectation // XCode crashes if we use the original expectation directly
         
         NSNotificationCenter.defaultCenter().postNotificationName(UIApplicationDidReceiveMemoryWarningNotification, object: nil)

    }
    
    func testRemoveImageInexisting() {
        let sut = MemoryCache()
        
        sut.removeImage("key")
    }
    
    func testOnMemoryWarning() {
        let sut = MemoryCache()
        let key = "key"
        sut.setImage(UIImage(), key)
        XCTAssertNotNil(sut.fetchImage(key))

    }
    
    func testFetchImageWithNilKey () {
        let sut = MemoryCache("test")
        
        XCTAssert(sut.fetchImage(nil) == nil, "nil key should returns nil image")
    }
    
    func testFetchImageEqualImage () {
        let sut = MemoryCache("test")
        
        let image = UIImage.imageWithColor(UIColor.cyanColor(), CGSizeMake(30, 30), true)
        let key = "key"
