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Light-Client
Implementation of the Light Client Verification and Fork Detection protocols.
Documentation
See documentation on crates.io.
Example
The code below demonstrates the main use case for the Tendermint Light Client: syncing to the latest block, verifying it, and performing fork detection.
Please refer to the light_client
example for fully working code.
let primary_instance: Instance = make_instance;
let witness_instance: Instance = make_instance;
let mut peer_addr = new;
peer_addr.insert;
peer_addr.insert;
let peer_list = builder
.primary
.witness
.build;
let mut supervisor = new;
let mut handle = supervisor.handle;
// Spawn the supervisor in its own thread.
spawn;
loop
Testing
The Tendermint Light Client is primarily tested through unit tests.
Core Verification
The logic for the core verification of light blocks is entirely self-contained in
the predicates
module. This code is exercised in a family
of tests called single_step
via a set of JSON fixtures
which encode an initial trusted state, a target block to verify, and the
expected result of the core verification algorithm.
These tests come in two flavours:
skipping
tests, where there is a gap between the initial trusted state and the target block.sequential
tests, where there the initial trusted state and the target block are adjacent.
The following command can be used to run only these tests:
Model-based tests
We started to employ model-based testing (MBT), which is currently limited to the core verification. In MBT, the testing procedure is based on the Light Client formal model, and the tests themselves are simple assertions in the modeling language TLA+. The current set of TLA+ tests is translated automatically into the set of JSON fixtures. Please refer to the MBT Guide, and the MBT Abstract for further information.
The following command can be used to run only these tests:
Bisection
Similarly to the core verification logic, the algorithm for performing bisecting verification is exercised via a set of JSON fixtures which encode an initial trusted state, a target block to verify, a set of intermediary blocks, and the expected result of the bisection algorithm.
These tests target the light_client
module,
and can be found in the tests/light_client.rs
file.
To run the tests:
Fork Detection
Similarly to the bisection algorithm, the fork detection algorithm is tested via a set of JSON fixtures which encode an initial trusted state, a target block to verify, a set of intermediary blocks, and the expected result of the fork detection algorithm.
These tests target the supervisor
module,
and can be found in the tests/supervisor.rs
file.
To run the tests:
Voting Power Calculator
The voting power calculator is exercised through unit tests which rely on JSON fixtures to provide the calculator with various types of light blocks together with the expected result of the computation.
The following command can be used to run only these tests:
Integration Tests
This project also includes simple integration test which spawns a light client instance against a single Tendermint full node which acts both as a primary peer and as its own witness.
Because this test requires a running Tendermint node, it is ignored by default. To run this test locally:
# In one terminal
# In another terminal
Other tests
A few core datastructures, such as the PeerList
implementation,
come with unit tests located in the same module as the implementation.
To run these tests together with all tests described above:
$ cargo test -p tendermint-light-client --all-features