public void Free()
{
var ram = new Ram(2, 1);
var pcb = new ProcessContextBlock {
Id = 1
};
var frame = ram.Allocate(pcb);
Assert.That(frame, Is.Not.Null);
frame = ram.Allocate(pcb);
Assert.That(frame, Is.Not.Null);
ram.Free(frame);
frame = ram.Allocate(pcb);
Assert.That(frame, Is.Not.Null);
}