add test to assert MapIterator failure against keyless (queues) maps

This commit introduces the `TestIterateWrongMap` test, which should
assert that the `MapIterator` fails while called on keyless maps such as
queues. We do not expect different behaviours, as the `MapIterator.Next`
relies on the presence of a key for which it lookups the value.
A different method can be later introduces to also traverse a queue, but
in that case we'd need to additionally remove the value.

Signed-off-by: Simone Magnani <simone.magnani@isovalent.com>

map_test.go

@@ -1126,6 +1126,29 @@ func TestMapIterate(t *testing.T) {
 	qt.Assert(t, qt.DeepEquals(keys, data))
 }
 
+func TestIterateWrongMap(t *testing.T) {
+	testutils.SkipOnOldKernel(t, "4.20", "map type queue")
+
+	m, err := NewMap(&MapSpec{
+		Type:       Queue,
+		ValueSize:  4,
+		MaxEntries: 2,
+	})
+	qt.Assert(t, qt.IsNil(err))
+	defer m.Close()
+
+	for _, v := range []uint32{0, 1} {
+		err := m.Put(nil, uint32(v))
+		qt.Assert(t, qt.IsNil(err))
+	}
+
+	var value uint32
+	entries := m.Iterate()
+
+	qt.Assert(t, qt.IsFalse(entries.Next(nil, &value)))
+	qt.Assert(t, qt.IsNotNil(entries.Err()))
+}
+
 func TestMapIteratorAllocations(t *testing.T) {
 	arr, err := NewMap(&MapSpec{
 		Type:       Array,