 			for i in [0...state.count]
 				localCache.del state.keys[i], (err, count) ->
 					state.n++
-					should(err).be.null()
+					should.not.exist err
 					0.should.eql count
 					return
 

		it "get previously set key", (done) ->
			localCache.get "zero", (err, res) ->
				state.n++
				should(err).be.null()
				0.should.eql res
				done()
				return

			for key in state.keys
				localCache.set key, state.value, 0, (err, res) ->
					state.n++
					should.not.exist err
					return
			return

		it "generate a sub-list of keys", () ->
			state.getKeys = state.keys.splice 50, 5
			return

		it "generate prediction", () ->
			state.prediction = {}
			for key in state.getKeys
				state.prediction[key] = state.value
			return
