EasyMock Void Method - expectLastCall()

Sometimes we want to mock void methods. EasyMock expect() method can’t be used to mock void methods. However, we can use expectLastCall() along with andAnswer() to mock void methods.

EasyMock void method

When we use expectLastCall() and andAnswer() to mock void methods, we can use getCurrentArguments() to get the arguments passed to the method and perform some action on it. Finally, we have to return null since we are mocking a void method. Let’s say we have a utility class as:

package com.journaldev.utils;

public class StringUtils {

	public void print(String s) {
		System.out.println(s);
	}
}

Here is the code to mock void method print() using EasyMock.

package com.journaldev.easymock;

import static org.easymock.EasyMock.*;

import org.junit.jupiter.api.Test;

import com.journaldev.utils.StringUtils;

public class EasyMockVoidMethodExample {

  @Test
  public void test() {
    StringUtils mock = mock(StringUtils.class);
    
    mock.print(anyString());
    expectLastCall().andAnswer(() -> {
      System.out.println("Mock Argument = "
          +getCurrentArguments()[0]);
      return null;
    }).times(2);
    replay(mock);
    
    mock.print("Java");
    mock.print("Python");
    verify(mock);
  }
}

Below image shows the console output when the above JUnit test is executed.

expectLastCall().andVoid()

If we just want to mock void method and don’t want to perform any logic, we can simply use expectLastCall().andVoid() right after calling void method on mocked object.

You can checkout complete project and more EasyMock examples from our GitHub Repository.