Testing apps for Metal L2

For the most part, running applications on Metal L2 is identical to running them on Ethereum, so the testing is identical too. In this guide, you learn the best practices for Metal L2 testing where there are differences.

Unit tests and single layer integration tests

The vast majority of tests do not involve any Metal L2-specific features. In those cases, while you could test everything on Metal L2 or a test network, that would normally be inefficient. Most Ethereum development stacks include features that make testing easier, which normal Ethereum clients, such as geth (and our modified version, op-geth) don't support. Therefore, it is a good idea to run the majority of tests, which do not rely on Metal L2-specific features, in the development stack. It is a lot faster.

It is a best practice to design and run thorough tests across an OP test network, either in your local development environment or on the test network, depending on your use case. Running proper testing is key to identifying fringe cases where the equivalence between Metal L2 and Ethereum breaks down (or where Ethereum mainnet itself and the development stack may be non-equivalent in a production environment).

Multilayer integration tests

Some apps need Metal L2-specific features that aren't available as part of the development stack. For example, if your decentralized application relies on inter-domain communication, the effort of developing a stub to let you debug it in a development stack is probably greater than the hassle of having the automated test go to a local development environment each time.

Integration with other products

In many cases a decentralized application requires the services of other contracts. For example, Perpetual v. 2 (opens in a new tab) cannot function without Uniswap v. 3 (opens in a new tab).

If that is the case you can use mainnet forking (opens in a new tab). It works with Metal L2. Alternatively, you can connect to our test network if those contracts are also deployed there (in many cases they are).