You don't need those voting for the bill to act in good faith if you have as part of the system of passing bills that the opposition gets to write the (adversarial part of the) test suite. Then either that forces any loopholes (or other undesirable effects) to be: updated as explicitly intended (with bad publicity and potential for reversion upon a change of government); or taken into account and the bill updated to reflect that, or left in the test case for case law to cite as intended.

Either way you really want intent to be encoded somehow.