gistfile1.java

public class MyPrinter implements MyPrinterInterface(){
  
  @Override
  public void printToScreen(String toPrint){
    System.out.println(toPrint);
  }
}

public class MyPrinterMock implements MyPrinterInterface(){
  
  private LinkedList<String> history = new LinkedList<String>();
  
  @Override
  public void printToScreen(String toPrint){
    history.push(toPrint);  
  }
  
  public Boolean lastCallWas(String message){
    return history.peek().equals(message);
  }
}