1. A method for providing a bitwise constraint for test generation, the method comprising: providing a language structure for expressing the bitwise constraint, said language structure including at least one constraint parameter and at least one operator, said constraint parameter being further constrained to an interval containing at least one value, said interval having interval limits; propagating information bi-directionally to determine interval limits for said constraint parameters at least partially according to the bitwise constraint; and computing one or more permissible values for the constraint parameter.