def setUp(self):
self.t1 = terms.string2Term("f(X, g(Y))")
self.t2 = terms.string2Term("a")
self.t3 = terms.string2Term("b")
self.t4 = terms.string2Term("f(a, g(a))")
self.t5 = terms.string2Term("f(a, g(b))")
self.sigma1 = Substitution([("X", self.t2), ("Y", self.t2)])
self.sigma2 = Substitution([("X", self.t2), ("Y", self.t3)])
def testBacktrack(self):
"""
Test backtrackable substitutions.
"""
sigma = BTSubst()
state = sigma.getState()
sigma.addBinding(('X', terms.string2Term("f(Y)")))
res = sigma.backtrackToState(state)
self.assertEqual(res, 1)
res = sigma.backtrack()
self.assertTrue(not res)