CODEWITHSUNDEEP
javajunitpowermockeasymock
speedos82
speedos82

Reputation: 97

PowerMock - How to call manipulate the parameters of a mocked method

I'm using PowerMock/EasyMock to test a static method in which one of the parameters is a StringBuffer that is appended to by a method in that mocked class.

This is a simplified class to demonstrate.

import java.util.Date;

public class ContentChanger
{
    public static int change(StringBuffer sb)
    {
        sb.append( new Date() );
        return 0;
    }
}

And here is the unit test...

import org.easymock.EasyMock;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.easymock.PowerMock;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(ContentChanger.class)
public class ContentChangerTest
{
    @Test
    public void test001()
    {
    // Declare an empty StringBuffer
    StringBuffer var = new StringBuffer();

    // Enable static mocking for the ContentChanger class
    PowerMock.mockStatic( ContentChanger.class );

    // Catch the call and send to test method
    EasyMock.expect(ContentChanger.change( var )).andDelegateTo( test(var) );

    // Replay all mock classes/methods
    PowerMock.replayAll();

    // Call the method to be mocked
    System.out.println( ContentChanger.change( var ) + " = " + var );
    }


    private int test( StringBuffer sb )
    {
        sb.append( "Mocked" );
        return 1;
    }
}

What I expect to happen is that the test method is called and the StringBuffer to output..

1 = MOCKED

But what is happening is the StringBuffer var is updated before the mocked method is called.

i.e. I get the following...

java.lang.AssertionError: 
  Unexpected method call ContentChanger.change(Mocked):
    ContentChanger.change(Mocked): expected: 1, actual: 2

Is there a way to invoke another class/method, to change the contents of the parameter when called instead of pre-replay.

Upvotes: 0

Views: 1835

Answers (1)

Henri
Henri

Reputation: 5731

The problem is that you are calling test(var). andDelegateTo expects an Object that will be of the same class/interface as the mock. See http://easymock.org/user-guide.html#verification-creating.

Since you are on a static method, this is not really possible. So the best is to use IAnswer instead. Here is the working code:

        EasyMock.expect(ContentChanger.change( var )).andAnswer(new IAnswer<Integer>() {
        @Override
        public Integer answer() throws Throwable {
            StringBuffer sb = (StringBuffer) EasyMock.getCurrentArguments()[0];
            sb.append( "Mocked" );
            return 1;
        }
    })

Upvotes: 1

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