In a TDD thread on tests as specifications there was a link to Uncle Bob talking about Stable State: An Emergent Rule, an excerpt is:
If you look carefully at the specification of the Bowling Game you will see that the state of the
Game is changed only by the
setup block within the
context blocks. The
specify blocks simply interrogate and verify state. This is in stark contrast to the JUnit tests in which the
test methods both change and verify the state of the
Really its the same idea as some people practicing BDD have, keep the test/specification methods small and preferably just doing Assertions (or mock verifications I guess).