Cross Chain

Usually, invariants are run on a single chain. However, Gate has the capability of getting some data sources from multiple chains.

Even if you test invariants against a specific block, the cross-chain sources will always be evaluated against the head of the specified chain.

Syntax

For supported data sources, simply add the chainId parameter:

source usdtSymbol = Call {
    contract: 0xc2132D05D31c914a87C6611C10748AEb04B58e8F,
    signature: "function signature() returns (string)",
    chainId: 137
};

This source would run on Polygon, even if the rest of the gate file itself runs on Ethereum.

Most sources also support RPC URL as chainId parameter:

source usdtSymbol = Call {
    contract: 0xc2132D05D31c914a87C6611C10748AEb04B58e8F,
    signature: "function signature() returns (string)",
    chainId: "https://rpc.mock.com"
};

This source would make RPCs against the specified URL.

Additionally, some non-EVM chains (without a numerical chain ID) can be specified as follows:

• Bitcoin Mainnet: chainId: "bitcoin"

• Bitcoin Signet: chainId: "signet"

• Starknet Mainnet: chainId: "starknet"

• Babylon Mainnet: chainId: "babylon-mainnet"

• Babylon Testnet: chainId: "babylon-testnet"

The chainId parameter is not required for sources that are meant to run on the primary chain the invariants are running on.

Supported sources

Currently, the following sources are cross-chain compatible:

• Balance

• Call

• HistoricalEvents*

• HistoricalCalls*

• ValidatorBalance*

• Slashings*

• StateRoot

• BlockHash

• StorageHash

* Does not support RPC URL