Added normalization tests for implications.

These tests ensure that implications are correctly reduced to
disjunctions in preconditions (nested and not) and goal descriptions.

tests/data/normalization/normalization-2.pddl

@@ -0,0 +1,49 @@
+; tests that “imply” statements in preconditions are correctly reduced
+(define (domain test-normalization)
+	(:predicates
+		(test-predicate-0)
+		(test-predicate-1 ?x)
+		(test-predicate-2 ?x ?y))
+
+	; top-level “imply” statement
+	(:action test-action-1
+		:parameters
+			(?x)
+		:precondition
+			(imply
+				(test-predicate-0)
+				(test-predicate-1 ?x))
+		:effect
+			(test-predicate-1 ?x))
+
+	; nested “imply” statement
+	(:action test-action-2
+		:parameters
+			(?x)
+		:precondition
+			(and
+				(and
+					(imply
+						(test-predicate-0)
+						(test-predicate-1 ?x))
+					(test-predicate-0))
+				(test-predicate-0))
+		:effect
+			(test-predicate-1 ?x))
+)
+
+(define (problem test-normalization)
+	(:domain test-normalization)
+
+	(:objects a b c)
+
+	(:init
+		(test-predicate-0))
+
+	; “imply” statement in goal
+	(:goal
+		(and
+			(imply
+				(test-predicate-0)
+				(test-predicate-1 a))
+			(test-predicate-0))))