changing values of a boolean field

Solution 1:

Create a public setter method

public class A{
  private String msg,
  private String name,
  private int number;
  private boolean isActive;

  public void setIsActive(boolean isActive) {
    this. isActive = isActive;
  }
}

You can call the setter from the test case since it's public.

case.setIsActive(false);