This is a basic example of an ERC-6900 compatible subscription plugin called SubscriptionPlugin, built in Foundry. Similar to services like Netflix, this plugin allows users to manage monthly subscriptions. It has one primary function that can be called through a user operation, called subscribe, which processes a user's subscription payment.
In the /src directory, you will find this plugin documented in detail to help you understand its functionality.
In the /test directory, there is a basic test demonstrating how the subscription plugin works. This will show you how to set up the modular account, install the plugins, and send a user operation that specifies the intent to subscribe or manage subscriptions. Use forge test to run these tests.
Also included is a helper contract for tests called AccountTestBase, which simplifies the process of setting up the EntryPoint and a testing account. If you're writing your own tests for a custom subscription plugin, you can use this test base to streamline your setup.
Feel free to modify the plugin and tests to deepen your understanding of ERC-6900 plugins, or use this as a starting point to create your own subscription plugin! Click "Use this template" above to create your own plugin.