Searched on google about, how to mock a variable in unit testing and seen some suggestions, for my case its not working. my scenario is,
class Keys {
private static Keys sKeys;
private String enKey = null;
static synchronized sKeys getInstance() {
    if(sKeys == null) {
        sKeys = new Keys();
    }
    return sKeys;
}
Boolean isLocked() {
    if(enKey == null ) {
        return true;
    }
    return false;
  }
}
This is the class, i have written. Unit test of the class is below,
@RunWith(MockitoJUnitRunner.class)     
public class KeysTest {
@Test
public void isLocked_Test() {
    Keys key = Keys.getInstance();
    Key.isLocked();
   // Here in isLocked function I want to mock the enKey value to other than null
   }
}
Here, i want to call isLocked function, and i want to set or mock the enKey variable value to other than null.
How i can do that? Could anyone help me on that?
 
    