Added a halt instruction test

creature_test.go

@@ -183,3 +183,19 @@ func TestPeekPoke(test *testing.T) {
 		test.Fail()
 	}
 }
+
+func TestHalt(test *testing.T) {
+	machine := runMachineTest ([]int {
+		PUSH, 32,
+		HALT,
+		PUSH, 3,
+	}, nil, test)
+	
+	result := machine.Pop()
+	test.Log("popped:", result)
+
+	if result != 32 {
+		test.Log("result should be", 32)
+		test.Fail()
+	}
+}