AIMA.Test.Core.Unit.Logic.FOL.UnifierTest.testTermEquality C# (CSharp) Method

        public void testTermEquality()
        {
            FOLDomain domain = new FOLDomain();
            domain.addConstant("A");
            domain.addConstant("B");
            domain.addFunction("Plus");

            FOLParser parser = new FOLParser(domain);

            TermEquality te1 = (TermEquality)parser.parse("x = x");
            TermEquality te2 = (TermEquality)parser.parse("x = x");

            // Both term equalities the same,
            // should unify but no substitutions.
            Dictionary<Variable, Term> result = unifier.unify(te1, te2);

            Assert.IsNotNull(result);
            Assert.AreEqual(0, result.Count);

            // Different variable names but should unify.
            te1 = (TermEquality)parser.parse("x1 = x1");
            te2 = (TermEquality)parser.parse("x2 = x2");

            result = unifier.unify(te1, te2);

            Assert.IsNotNull(result);
            Assert.AreEqual(1, result.Count);
            Assert.AreEqual("{x1=x2}", result.ToString());

            // Test simple unification with reflexivity axiom
            te1 = (TermEquality)parser.parse("x1 = x1");
            te2 = (TermEquality)parser.parse("Plus(A,B) = Plus(A,B)");

            result = unifier.unify(te1, te2);

            Assert.IsNotNull(result);

            Assert.AreEqual(1, result.Count);
            Assert.AreEqual("{x1=Plus(A,B)}", result.ToString());

            // Test more complex unification with reflexivity axiom
            te1 = (TermEquality)parser.parse("x1 = x1");
            te2 = (TermEquality)parser.parse("Plus(A,B) = Plus(A,z1)");

            result = unifier.unify(te1, te2);

            Assert.IsNotNull(result);

            Assert.AreEqual(2, result.Count);
            Assert.AreEqual("{x1=Plus(A,B), z1=B}", result.ToString());

            // Test reverse of previous unification with reflexivity axiom
            // Should still be the same.
            te1 = (TermEquality)parser.parse("x1 = x1");
            te2 = (TermEquality)parser.parse("Plus(A,z1) = Plus(A,B)");

            result = unifier.unify(te1, te2);

            Assert.IsNotNull(result);

            Assert.AreEqual(2, result.Count);
            Assert.AreEqual("{x1=Plus(A,B), z1=B}", result.ToString());

            // Test with nested terms
            te1 = (TermEquality)parser
                    .parse("Plus(Plus(Plus(A,B),B, A)) = Plus(Plus(Plus(A,B),B, A))");
            te2 = (TermEquality)parser
                    .parse("Plus(Plus(Plus(A,B),B, A)) = Plus(Plus(Plus(A,B),B, A))");

            result = unifier.unify(te1, te2);

            Assert.IsNotNull(result);

            Assert.AreEqual(0, result.Count);

            // Simple term equality unification fails
            te1 = (TermEquality)parser.parse("Plus(A,B) = Plus(B,A)");
            te2 = (TermEquality)parser.parse("Plus(A,B) = Plus(A,B)");

            result = unifier.unify(te1, te2);

            Assert.IsNull(result);
        }