Improved output of negated literals and added unit test.

tests/TestTranslation.cpp

@@ -120,4 +120,12 @@ TEST_CASE("[translation] Rules are translated correctly", "[translation]")
 
 		REQUIRE(output.str() == "V1 in X and V2 in (1,) and exists X1, X2 (X1 in X and X2 in (2,) and q(X1, X2)) -> p(V1, V2)\n");
 	}
+
+	SECTION("single negation")
+	{
+		input << "not p(X, 1) :- not q(X, 2).";
+		anthem::translate("input", input, context);
+
+		REQUIRE(output.str() == "V1 in X and V2 in 1 and exists X1, X2 (X1 in X and X2 in 2 and not q(X1, X2)) -> not p(V1, V2)\n");
+	}
 }