Cannot Find property after adding it with hook_entity_property_info_alter (callback not firing)
I think this is what's going on...

With your current code you've described the property to the entity API module; if you want to access it via that you already can:

$node = node_load($nid);
$wrapper = entity_metadata_wrapper('node', $node);
print $wrapper-&gt;test_property-&gt;value(); // Prints '10'


But the core entity system has no knowledge of test_property, so it doesn't show up on a node object from node_load(). To get it there, you'll need to implement hook_node_load():

function mymodule_node_load($nodes, $types) {
  foreach ($nodes as $node) {
    if ($type == 'mynode') {
      $node-&gt;test_property = mymodule_test_property_getter_callback($node);
    }
  }
}


There's also the outside chance that your getter callback will rely on something having been added to the node object already, by another module's implementation of hook_node_load(). You can get past that by moving your implementation to last in the queue, with hook_module_implements_alter().

If you want Views support, I think you'll also need to implement hook_views_data_alter() to add the property to the node table. But maybe the entity module will magic that up for you, it's a good'un.