# Blockchain Tests¶

Found in /BlockTests, the blockchain tests aim is to test the basic verification of a blockchain.

/BlockTests - general blockchain tests. All blocks are built on network: Frontier /BlockTests/Homestead - homestead blockchain tests. All blocks are built on network: Homestead /BlockTests/TestNetwork - transition blockchain tests. All blocks before 5th are built on network: Frontier, then each block should correspond to Homestead rules.

It is based around the notion of executing a list of single blocks, described by the blocks portion of the test. The first block is the modified genesis block as described by the genesisBlockHeader portion of the test. A set of pre-existing accounts are detailed in the pre portion and form the world state of the genesis block.

It is generally expected that the test implementer will read genesisBlockHeader and pre and build the corresponding blockchain in the client. Then the new blocks, described by its RLP found in the rlp object of the blocks (RLP of a complete block, not the block header only), is read. If the client concludes that the block is valid, it should execute the block and verify the parameters given in blockHeader (block header of the new block), transactions (transaction list) and uncleHeaders (list of uncle headers). If the client concludes that the block is invalid, it should verify that no blockHeader, transactions or uncleHeaders object is present in the test. The client is expected to iterate through the list of blocks and ignore invalid blocks.

## Basic structure¶

{
"ValidBlocks": {
"pre": { ... },
"blocks" : [
{
"chainname" : "A",
"blocknumber" : "1",
"rlp": { ... },
"transactions": { ... },
},
{
"chainname" : "A",
"blocknumber" : "2",
"rlp": { ... },
"transactions": { ... },
}
]
},
"SomeInvalidBlocks": {
"pre": { ... },
"blocks" : [
{
"chainname" : "B",
"blocknumber" : "3",
"chainnetwork" : "Frontier",
"rlp": { ... },
},
{
"blocknumber" : "1",
"rlp": { ... },
"transactions": { ... },
},
{
"blocknumber" : "1",
"rlp": { ... },
},
{
"blocknumber" : "2",
"rlp": { ... },
"transactions": { ... },
}
]
},
...
}


## Sections¶

• The genesisBlockHeader section
coinbase:
The 160-bit address to which all fees collected from the successful mining of this block be transferred, as returned by the COINBASE instruction.
difficulty:
A scalar value corresponding to the difficulty level of this block. This can be alculated from the previous block’s difficulty level and the timestamp, as returned by the DIFFICULTY instruction.
gasLimit:
A scalar value equal to the current limit of gas expenditure per block, as returned by the GASLIMIT instruction.
number:
A scalar value equal to the number of ancestor blocks. The genesis block has a number of zero.
timestamp:
A scalar value equal to the reasonable output of Unix’s time() at this block’s inception, as returned by the TIMESTAMP instruction.
parentHash:
The Keccak 256-bit hash of the parent block’s header, in its entirety
bloom:
The Bloom filter composed from indexable information (logger address and log topics) contained in each log entry from the receipt of each transaction in the transactions list.
extraData:
An arbitrary byte array containing data relevant to this block. This must be 1024 bytes or fewer.
gasUsed:
A scalar value equal to the total gas used in transactions in this block.
nonce:
A 256-bit hash which proves that a sufficient amount of computation has been carried out on this block.
receiptTrie:
The Keccak 256-bit hash of the root node of the trie structure populated with the receipts of each transaction in the transactions list portion of the block.
stateRoot:
The Keccak 256-bit hash of the root node of the state trie, after all transactions are executed and finalisations applied.
transactionsTrie:
The Keccak 256-bit hash of the root node of the trie structure populated with each transaction in the transactions list portion of the block.
uncleHash:
The Keccak 256-bit hash of the uncles list portion of this block
• pre section: as described in State Tests.
• postState section: as described in State Tests (section - post).
• blocks section is a list of block objects, which have the following format:
• rlp section contains the complete rlp of the new block as described in the yellow paper in section 4.3.3.
• blockHeader section describes the block header of the new block in the same format as described in genesisBlockHeader.
• transactions section is a list of transactions which have the same format as in Transaction Tests.
• uncleHeaders section is a list of block headers which have the same format as descibed in genesisBlockHeader.

## Optional BlockHeader Sections (Information fields)¶

"blocknumber" = "int" is section which defines what is the order of this block. It is used to define a situation when you have 3 blocks already imported but then it comes new version of the block 2 and 3 and thus you might have new best blockchain with blocks 1 2’ 3’ instead previous. If blocknumber is undefined then it is assumed that blocks are imported one by one. When running test, this field could be used for information purpose only.

"chainname" = "string" This is used for defining forks in the same test. You could mine blocks to chain “A”: 1, 2, 3 then to chain “B”: 1, 2, 3, 4 (chainB becomes primary). Then again to chain “A”: 4, 5, 6 (chainA becomes primary) and so on. chainname could also be defined in uncle header section. If defined in uncle header it tells on which chain’s block uncle header would be populated from. When running test, this field could be used for information purpose only.

"chainnetwork" = "string" Defines on which network rules this block was mined. (see the difference https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki). When running test, this field could be used for information purpose only.