eth2.0-specs/tests/formats/fork_choice/README.md

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# Fork choice tests
The aim of the fork choice tests is to provide test coverage of the various components of the fork choice.
## Test case format
### `meta.yaml`
```yaml
description: string -- Optional. Description of test case, purely for debugging purposes.
bls_setting: int -- see general test-format spec.
```
### `anchor_state.ssz_snappy`
An SSZ-snappy encoded `BeaconState`, the state to initialize store with `get_forkchoice_store(anchor_state: BeaconState, anchor_block: BeaconBlock)` helper.
### `anchor_block.ssz_snappy`
An SSZ-snappy encoded `BeaconBlock`, the block to initialize store with `get_forkchoice_store(anchor_state: BeaconState, anchor_block: BeaconBlock)` helper.
### `steps.yaml`
The steps to execute in sequence. There may be multiple items of the following types:
#### `on_tick` execution step
The parameter that is required for executing `on_tick(store, time)`.
```yaml
{
tick: int -- to execute `on_tick(store, time)`.
valid: bool -- optional, default to `true`.
If it's `false`, this execution step is expected to be invalid.
}
```
After this step, the `store` object may have been updated.
#### `on_attestation` execution step
The parameter that is required for executing `on_attestation(store, attestation)`.
```yaml
{
attestation: string -- the name of the `attestation_<32-byte-root>.ssz_snappy` file.
To execute `on_attestation(store, attestation)` with the given attestation.
valid: bool -- optional, default to `true`.
If it's `false`, this execution step is expected to be invalid.
}
```
The file is located in the same folder (see below).
After this step, the `store` object may have been updated.
#### `on_block` execution step
The parameter that is required for executing `on_block(store, block)`.
```yaml
{
block: string -- the name of the `block_<32-byte-root>.ssz_snappy` file.
To execute `on_block(store, block)` with the given attestation.
valid: bool -- optional, default to `true`.
If it's `false`, this execution step is expected to be invalid.
}
```
The file is located in the same folder (see below).
After this step, the `store` object may have been updated.
#### `on_merge_block` execution
Adds `PowBlock` data which is required for executing `on_block(store, block)`.
```yaml
{
pow_block: string -- the name of the `pow_block_<32-byte-root>.ssz_snappy` file.
To be used in `get_pow_block` lookup
}
```
The file is located in the same folder (see below).
PowBlocks should be used as return values for `get_pow_block(hash: Hash32) -> PowBlock` function if hashes match.
#### Checks step
The checks to verify the current status of `store`.
```yaml
checks: {<store_attibute>: value} -- the assertions.
```
`<store_attibute>` is the field member or property of [`Store`](../../../specs/phase0/fork-choice.md#store) object that maintained by client implementation. Currently, the possible fields included:
```yaml
head: {
slot: int,
root: string, -- Encoded 32-byte value from get_head(store)
}
time: int -- store.time
genesis_time: int -- store.genesis_time
justified_checkpoint: {
epoch: int, -- Integer value from store.justified_checkpoint.epoch
root: string, -- Encoded 32-byte value from store.justified_checkpoint.root
}
finalized_checkpoint: {
epoch: int, -- Integer value from store.finalized_checkpoint.epoch
root: string, -- Encoded 32-byte value from store.finalized_checkpoint.root
}
best_justified_checkpoint: {
epoch: int, -- Integer value from store.best_justified_checkpoint.epoch
root: string, -- Encoded 32-byte value from store.best_justified_checkpoint.root
}
```
For example:
```yaml
- checks:
time: 192
head: {slot: 32, root: '0xdaa1d49d57594ced0c35688a6da133abb086d191a2ebdfd736fad95299325aeb'}
justified_checkpoint: {epoch: 3, root: '0xc25faab4acab38d3560864ca01e4d5cc4dc2cd473da053fbc03c2669143a2de4'}
finalized_checkpoint: {epoch: 2, root: '0x40d32d6283ec11c53317a46808bc88f55657d93b95a1af920403187accf48f4f'}
best_justified_checkpoint: {epoch: 3, root: '0xc25faab4acab38d3560864ca01e4d5cc4dc2cd473da053fbc03c2669143a2de4'}
```
*Note*: Each `checks` step may include one or multiple items. Each item has to be checked against the current store.
### `attestation_<32-byte-root>.ssz_snappy`
`<32-byte-root>` is the hash tree root of the given attestation.
Each file is an SSZ-snappy encoded `Attestation`.
### `block_<32-byte-root>.ssz_snappy`
`<32-byte-root>` is the hash tree root of the given block.
Each file is an SSZ-snappy encoded `SignedBeaconBlock`.
## Condition
1. Deserialize `anchor_state.ssz_snappy` and `anchor_block.ssz_snappy` to initialize the local store object by with `get_forkchoice_store(anchor_state, anchor_block)` helper.
2. Iterate sequentially through `steps.yaml`
- For each execution, look up the corresponding ssz_snappy file. Execute the corresponding helper function on the current store.
- For the `on_block` execution step: if `len(block.message.body.attestations) > 0`, execute each attestation with `on_attestation(store, attestation)` after executing `on_block(store, block)`.
- For each `checks` step, the assertions on the current store must be satisfied.