Enums can be useful to compare different states of a type, for example if status == OrderStatus::Pending. However, you can not directly compare two enums for equality.

For this to work, you need to implement the PartialEq trait for the enum.

This can be done manually, but Rust provides a convenient way to implement the PartialEq trait for types using the derive attribute. This allows you to compare instances of a type for equality without manually implementing the trait.

In this challenge, you'll define a simple enum and use #[derive(PartialEq)] to automatically implement equality checks.

1. Define an enum OrderStatus with the following variants:

   • Pending — a unit variant representing an order that is not yet processed.
   • Shipped — a unit variant representing an order that has been shipped.
   • Cancelled(String) — a tuple variant with a reason for cancellation.

2. Use the #[derive(PartialEq)] attribute to derive the PartialEq trait for the enum.

3. Write tests to ensure that the derived implementation works as expected.

1. Use the #[derive(PartialEq)] macro for the OrderStatus enum.
2. Write tests to verify the equality and inequality of the enum variants.