Test Account Trie Structure

Documentation for tests/mpt/test_account_trie_structure.py@02aafd78.

Generate fixtures for these test cases for Bogota with:

fill -v tests/mpt/test_account_trie_structure.py --fork Bogota

Exercise the Merkle Patricia Trie via account addresses.

The account trie adds bookkeeping to the node operations the storage tests cover: accounts are deleted and re-created, each leaf value carries a storage root, and every block touches accounts the test does not choose (sender, coinbase, system contracts). The tests use mined addresses (*_ADDRS_* in constants.py).

Because of those accounts, shape assertions run over pre, which holds the whole genesis of the fixture being filled (plus the coinbase after the block), and pin only the nodes around the mined group; an uncontrolled account sharing the group's prefix fails the fill.

A committed account leaf can only be deleted by a contract created in the same transaction (EIP-6780). The deletion tests fund a mined address at genesis and CREATE2 onto it through the deterministic factory with init code that self-destructs at once: creation at a balance-only address is legal, and the contract counts as created in the transaction. The init code sends the balance to the sender, because from EIP-8246 a self-destructed account keeps its balance and is removed only when that balance is zero (EIP-161).

Not expressible: emptying a committed storage trie in one step while its account survives, and clearing a committed empty account (the filler emits no empty genesis accounts). CREATE2 onto an address that holds storage is out of scope.

Test Functions Overview

Name	Type	Cases (Bogota)	Description
test_account_deleted_and_recreated_same_block	blockchain_test	1	Delete a leaf and re-create it by a value transfer in the same block.
test_code_hash_flip_with_account_shape_change	blockchain_test	1	Code is deployed onto the collapse survivor, a balance-only account.
test_delete_and_update_survivor_same_block	blockchain_test	1	Delete one sibling and credit the other within one block.
test_delete_collapses_under_controlled_parent	state_test	6	Delete one child of a 2-child branch below a mined parent node.
test_delete_from_three_child_branch	state_test	1	Delete one of three accounts under one branch.
test_delete_resurrect_delete_across_blocks	blockchain_test	1	Delete a leaf, re-create it by a transfer, delete it again.
test_genesis_extension_and_branch	state_test	1	Two funded addresses sharing four nibbles sit under one branch.
test_genesis_full_branch_arity_sixteen	state_test	1	Sixteen funded addresses sharing four nibbles fill one branch.
test_insert_full_branch_during_execution	state_test	1	A contract pays sixteen mined addresses, creating their leaves.
test_mass_delete_sixteen_to_one	blockchain_test	1	Delete fifteen of sixteen accounts under one branch in one block.
test_resurrection_via_withdrawal	blockchain_test	2	Delete a leaf, then a withdrawal targets its address in the same block.
test_storage_root_flip_with_account_shape_change	blockchain_test	2	The collapse survivor is a contract whose storage root flips.
test_touched_empty_account_never_persists	state_test	1	A zero-value call to a never-seen address creates no leaf.