check total number of slots requested

beacon/goclient/attest_test.go

@@ -230,6 +230,8 @@ func TestGoClient_GetAttestationData(t *testing.T) {
 		require.Equal(t, gotResult1c.Target.Epoch, gotResult1a.Target.Epoch)
 		require.Equal(t, gotResult1c.Target.Root, gotResult1a.Target.Root)
 
+		uniqueSlots := serverGotRequests.SlowLen()
+		require.Equal(t, 2, uniqueSlots)
 		reqCntSlot1, ok := serverGotRequests.Get(slot1)
 		require.True(t, ok)
 		require.Equal(t, 1, reqCntSlot1)
@@ -300,5 +302,7 @@ func TestGoClient_GetAttestationData(t *testing.T) {
 			reqCnt, _ := serverGotRequests.GetOrSet(slot, 1)
 			require.Equal(t, 1, reqCnt)
 		}
+		uniqueSlots := serverGotRequests.SlowLen()
+		require.Equal(t, slotsTotalCnt, uniqueSlots)
 	})
 }

utils/hashmap/hashmap.go

@@ -38,6 +38,9 @@ func (m *Map[Key, Value]) Set(key Key, value Value) {
 }
 
 // SlowLen returns the number of elements in the map by iterating over all items.
+// This method call doesn't block other operations (for example Set), hence the
+// resulting length value returned might or might not reflect the outcome of
+// concurrent operations happening with this Map.
 //
 // This implementation is quite expensive. If it becomes a bottleneck,
 // we should consider maintaining an internal atomic counter and