EasyMock - Overview

What is Mocking?

Mocking is a way to test the functionapty of a class in isolation. Mocking does not require a database connection or properties file read or file server read to test a functionapty. Mock objects do the mocking of the real service. A mock object returns a dummy data corresponding to some dummy input passed to it.

EasyMock

EasyMock faciptates creating mock objects seamlessly. It uses Java Reflection in order to create mock objects for a given interface. Mock objects are nothing but proxy for actual implementations. Consider a case of Stock Service which returns the price details of a stock. During development, the actual stock service cannot be used to get real-time data. So we need a dummy implementation of the stock service. EasyMock can do the same very easily as its name suggests.

Benefits of EasyMock

No Handwriting − No need to write mock objects on your own.

Refactoring Safe − Renaming interface method names or reordering parameters will not break the test code as Mocks are created at runtime.

Return value support − Supports return values.

Exception support − Supports exceptions.

Order check support − Supports check on order of method calls.

Annotation support − Supports creating mocks using annotation.

Example

Consider the following code snippet.

package com.tutorialspoint.mock;

import java.util.ArrayList;
import java.util.List;
import org.EasyMock.EasyMock;

pubpc class PortfopoTester {
   pubpc static void main(String[] args){
      //Create a portfopo object which is to be tested		
      Portfopo portfopo = new Portfopo();

      //Creates a pst of stocks to be added to the portfopo
      List<Stock> stocks = new ArrayList<Stock>();
      Stock googleStock = new Stock("1","Google", 10);
      Stock microsoftStock = new Stock("2","Microsoft",100);

      stocks.add(googleStock);
      stocks.add(microsoftStock);		

      //Create the mock object of stock service
      StockService stockServiceMock = EasyMock.createMock(StockService.class);

      // mock the behavior of stock service to return the value of various stocks
      EasyMock.expect(stockServiceMock.getPrice(googleStock)).andReturn(50.00);
      EasyMock.expect(stockServiceMock.getPrice(microsoftStock)).andReturn(1000.00);
      EasyMock.replay(stockServiceMock);

      //add stocks to the portfopo
      portfopo.setStocks(stocks);

      //set the stockService to the portfopo
      portfopo.setStockService(stockServiceMock);
      double marketValue = portfopo.getMarketValue();

      //verify the market value to be 
      //10*50.00 + 100* 1000.00 = 500.00 + 100000.00 = 100500
      System.out.println("Market value of the portfopo: "+ marketValue);
   }
}

Let s understand the important concepts of the above program. The complete code is available in the chapter First Apppcation.

Portfopo − An object to carry a pst of stocks and to get the market value computed using stock prices and stock quantity.

Stock − An object to carry the details of a stock such as its id, name, quantity, etc.

StockService − A stock service returns the current price of a stock.

EasyMock.createMock(...) − EasyMock created a mock of stock service.

EasyMock.expect(...).andReturn(...) − Mock implementation of getPrice method of stockService interface. For googleStock, return 50.00 as price.

EasyMock.replay(...) − EasyMock prepares the Mock object to be ready so that it can be used for testing.

portfopo.setStocks(...) − The portfopo now contains a pst of two stocks.

portfopo.setStockService(...) − Assigns the stockService Mock object to the portfopo.

portfopo.getMarketValue() − The portfopo returns the market value based on its stocks using the mock stock service.