public void StreamWalkTests()
{
Stream stream = new Stream();
// Const value
Assert.AreEqual(Pair.Value("test"), stream.Walk(Pair.Value("test")));
// Variable -> Value
Pair a = Pair.Fresh();
Stream newStream = stream.AddAssociation(a, Pair.Value("test"));
Assert.AreEqual(newStream.Walk(a.key), "test");
// Variable -> Assigned variable
Pair b = Pair.Fresh();
newStream = newStream.AddAssociation(b, a);
Assert.AreEqual(newStream.Walk(b.key), "test");
// Variable -> Unassigned variable
Stream newStream2 = new Stream();
newStream2 = stream.AddAssociation(a, b);
Assert.AreEqual(newStream2.Walk(a), b);
}