Added a test for the entity lookup and fixed a bug found through that test.

core/build-config/tests.txt

@@ -1,2 +1,3 @@
 tests/internal/basic-tag-registry-usage
+tests/internal/entity-lookup
 tests/interface/entity-creation

core/inc-c/state.h

@@ -23,6 +23,6 @@ void mt_cleanup(MtState *state);
 void mt_start(MtState *state);
 
 MtEntity * mt_summon(MtState *state);
-void mt_delete(MtEntity *entity);
+void mt_drop(MtEntity *entity);
 
 #endif // MT_STATE_H

core/src-c/entity_lookup.c

@@ -31,6 +31,7 @@ MtEntity * mt_create_entity(void *state_voidptr, u32_t identifier)
     {
         entity = mt_allocate_entity_pool_slot(&state->entity_registry.pool);
         entity->parent_state = state;
+        entity->identifier = identifier;
         level3->entities[identifier & 0xff] = entity;
     }
     return entity;

core/tests/internal/entity-lookup/main.c

@@ -0,0 +1,19 @@
+#include <state.h>
+#include <entity.h>
+
+#include <stdio.h>
+
+int main(int argc, char **argv)
+{
+    MtState *state = mt_initialize("Interface Test");;
+    MtEntity *entity = mt_summon(state);
+    MtEntity *looked_up_entity = mt_get_entity(state, entity->identifier);
+
+    if(entity != looked_up_entity)
+        printf("Failed looking up entity; the pointers don't match:\nOriginal:   %p\nLooked Up:  %p\n", entity, looked_up_entity);
+    else
+        puts("The entity which was looked up from the identifier does match the original. SUCCESS!");
+
+    mt_drop(entity);
+    mt_cleanup(state);
+}