Remove truth tests and implement NullTest in terms of the base test.
Remove truth tests and implement NullTest in terms of the base test.

simonwagner/grantlee,cutelyst/grantlee,simonwagner/grantlee,cutelyst/grantlee,simonwagner/grantlee,simonwagner/grantlee,simonwagner/grantlee,cutelyst/grantlee,cutelyst/grantlee,simonwagner/grantlee,cutelyst/grantlee