-added some tests

-improved test runner

tests/id_manager.d

@@ -0,0 +1,36 @@
+module tests.id_manager;
+
+import ecs.id_manager;
+import ecs.entity;
+
+unittest
+{
+    IDManager manager;
+    manager.initialize();
+    EntityID id1 = manager.getNewID();
+    EntityID id2 = manager.getNewID();
+    EntityID id3 = manager.getNewID();
+
+    assert(id1 == EntityID(1, 0));
+    assert(id2 == EntityID(2, 0));
+    assert(id3 == EntityID(3, 0));
+
+    manager.optimize();
+    manager.releaseID(id2);
+    manager.releaseID(id1);
+
+    id2 = manager.getNewID();
+    id1 = manager.getNewID();
+
+    Entity e;
+    e.id = id3;
+    manager.update(e);
+
+    assert(id1 == EntityID(2, 1));
+    assert(id2 == EntityID(1, 1));
+    assert(id3 == EntityID(3, 0));
+    assert(manager.isExist(id3));
+    assert(!manager.isExist(EntityID(1, 0)));
+    assert(!manager.isExist(EntityID(0, 0)));
+    manager.deinitialize();
+}