Mock private field and private method using PowerMock

Example 

public class PrivateObject {

    private String privateString;

    public PrivateObject(String privateString) {
this.privateString = privateString;
    }

    private String getPrivateString() {
return this.privateString;
    }

}

Mock using PowerMock

// class instance

PrivateObject instance = new PrivateObject ();

// mock private field/variable

MemberModifier

                .field(PrivateObject .class, "privateString").set(

instance , "hellomock");

// mock private method

MemberModifier

.stub(MemberMatcher.method(PrivateObject .class,

"getPrivateString"))

.toReturn(

"Power Mock");