Hello.
I am developing a software oriented control of a manufacturing system. Precisely, I am modeling a machine that works workpieces. This machine is represented by a java class and his skeleton is the following:

public class VMM
{
private boolean on;
private boolean atUp;
private boolean atBottom;

public VMM()
{

}

public void goUp()
{

}

public void goBottom()
{

}

private void processWorkpiece()
{

}
}

Each method operate to the system state and therefore, it operate on his attributes that are:

boolean on;
boolean atUp;
boolean atBottom;


I have to perform Unit Tests of this class using JUnit. The problem is that in this case the aim is not to test each method, but the sequence with which these methods are called.
Somebody knows how I can perform these Unit Tests?