Added test for the metrics

include/dynamix/object_type_info.hpp

@@ -100,7 +100,7 @@ class DYNAMIX_API object_type_info : private mixin_collection
 
 #if DYNAMIX_ADDITIONAL_METRICS
     // number of living objects with this type info
-    mutable size_t num_objects;
+    mutable size_t num_objects = 0;
 #endif
 
     // this should be called after the mixins have been initialized

test/metrics.cpp

@@ -0,0 +1,82 @@
+// DynaMix
+// Copyright (c) 2013-2017 Borislav Stanimirov, Zahary Karadjov
+//
+// Distributed under the MIT Software License
+// See accompanying file LICENSE.txt or copy at
+// https://opensource.org/licenses/MIT
+//
+#include <dynamix/dynamix.hpp>
+
+#include "mutation_rules/test_mixins.hpp"
+
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest/doctest.h"
+
+TEST_SUITE("obj optional metrics");
+
+using namespace dynamix;
+
+TEST_CASE("metrics")
+{
+    object o1;
+
+    auto& mta = _dynamix_get_mixin_type_info((a*)(nullptr));
+    auto& mtb = _dynamix_get_mixin_type_info((b*)(nullptr));
+    auto& mtc = _dynamix_get_mixin_type_info((c*)(nullptr));
+
+    CHECK(mta.num_mixins == 0);
+    CHECK(mtb.num_mixins == 0);
+    CHECK(mtc.num_mixins == 0);
+
+    mutate(o1)
+        .add<a>()
+        .add<b>();
+
+    auto t1 = o1._type_info;
+
+    CHECK(t1->num_objects == 1);
+    CHECK(mta.num_mixins == 1);
+    CHECK(mtb.num_mixins == 1);
+    CHECK(mtc.num_mixins == 0);
+
+    o1.clear();
+
+    CHECK(t1->num_objects == 0);
+    CHECK(mta.num_mixins == 0);
+    CHECK(mtb.num_mixins == 0);
+    CHECK(mtc.num_mixins == 0);
+
+    object o2;
+
+    mutate(o2)
+        .add<a>()
+        .add<b>();
+
+    CHECK(t1->num_objects == 1);
+    CHECK(mta.num_mixins == 1);
+    CHECK(mtb.num_mixins == 1);
+    CHECK(mtc.num_mixins == 0);
+
+    mutate(o1)
+        .add<a>()
+        .add<b>();
+
+    CHECK(t1->num_objects == 2);
+    CHECK(mta.num_mixins == 2);
+    CHECK(mtb.num_mixins == 2);
+    CHECK(mtc.num_mixins == 0);
+
+    mutate(o1)
+        .remove<a>()
+        .add<c>();
+
+    auto t2 = o1._type_info;
+
+    CHECK(t1->num_objects == 1);
+    CHECK(t2->num_objects == 1);
+    CHECK(mta.num_mixins == 1);
+    CHECK(mtb.num_mixins == 2);
+    CHECK(mtc.num_mixins == 1);
+
+}
+