You can check the documentation here: https://docs.neutron.org/
You can check out the build instructions here: https://docs.neutron.org/neutron/build-and-run/overview
bash contrib/statesync.bash
You can check out the example contracts here: https://github.com/neutron-org/neutron-contracts
Integration tests are implemented here: https://github.com/neutron-org/neutron-integration-tests