test: Test that low difficulty chain fork is rejected

test/functional/test_runner.py

@@ -195,6 +195,7 @@ BASE_SCRIPTS = [
     'feature_uacomment.py',
     'wallet_coinbase_category.py',
     'feature_filelock.py',
+    'p2p_dos_header_tree.py',
     'p2p_unrequested_blocks.py',
     'feature_includeconf.py',
     'rpc_deriveaddresses.py',