[#51] policy: Fix tests

We don't want to return Null from contract when list is empty
because generated policy client cannot parse this.

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

policy/policy_contract.go

@@ -68,22 +68,10 @@ func RemoveChainsByPrefix(entity Kind, entityName string, name string) {
 // ListChains lists all chains for the namespace by prefix.
 // container may be empty.
 func ListChains(namespace, container, name string) [][]byte {
-	ctx := storage.GetReadOnlyContext()
-
-	var result [][]byte
-
-	prefixNs := storageKey(Namespace, namespace, name)
-	it := storage.Find(ctx, prefixNs, storage.ValuesOnly)
-	for iterator.Next(it) {
-		result = append(result, iterator.Value(it).([]byte))
-	}
+	result := ListChainsByPrefix(Namespace, namespace, name)
 
 	if container != "" {
-		prefixCnr := storageKey(Container, container, name)
-		it = storage.Find(ctx, prefixCnr, storage.ValuesOnly)
-		for iterator.Next(it) {
-			result = append(result, iterator.Value(it).([]byte))
-		}
+		result = append(result, ListChainsByPrefix(Container, container, name)...)
 	}
 
 	return result

tests/policy_test.go

@@ -89,12 +89,6 @@ func checkChainsByPrefix(t *testing.T, e *neotest.ContractInvoker, kind byte, en
 func checksChainsOnStack(t *testing.T, s *vm.Stack, expected [][]byte) {
 	require.Equal(t, 1, s.Len())
 
-	if len(expected) == 0 {
-		_, ok := s.Pop().Item().(stackitem.Null)
-		require.True(t, ok)
-		return
-	}
-
 	var actual [][]byte
 	arr := s.Pop().Array()
 	for i := range arr {