The following tree is successfully parsed by BT::BehaviorTreeFactory::createTreeFromText when I would have expected parsing to fail.

<root main_tree_to_execute="MainTree">
  <BehaviorTree ID="MainTree">
    <ForceSuccess>
    </ForceSuccess>
  </BehaviorTree>
</root>

Below is a test that verifies it's parsing incorrectly.

TEST(BehaviorTreeFactory, DecoratorWithoutChildThrows)
{
    BehaviorTreeFactory factory;
    const std::string tree_xml = R"(
<root>
    <BehaviorTree ID="Main">
        <ForceSuccess>
        </ForceSuccess>
    </BehaviorTree>
</root>
)";

    ASSERT_THROW(factory.createTreeFromText(tree_xml), BehaviorTreeException);
}

Output:

[ RUN      ] BehaviorTreeFactory.DecoratorWithoutChildThrows
/home/adam/src/BehaviorTree.CPP/tests/gtest_factory.cpp:375: Failure
Expected: factory.createTreeFromText(tree_xml) throws an exception of type BehaviorTreeException.
  Actual: it throws nothing.
[  FAILED  ] BehaviorTreeFactory.DecoratorWithoutChildThrows (2 ms)

Notes:

This caused a segmentation fault in our system as the returned BT::Tree has a decorator node with a nullptr child by default, so a tree.rootNode()->executeTick() crashes

The XML parsing logic has a validity check, but the decorator check for 1 child only works if the XML element's name "Decorator". When writing a tree like above, the XML element's name is "ForceSuccess"