Transfer Extrinsic

We will build the transfer extrinsic over two steps. In this step, we will just step up the skeleton of the extrinsic, the internal function, and the event that will be emitted at the end of the extrinsic.

Clean Code

It's been a while since we started programming using the initial template provided by this tutorial.

In that template, we already scaffolded for you the create_kitty extrinsic, the mint internal function, and the Created event.

In this step, we will be doing the same thing, but for a new extrinsic transfer.

To keep our code clean, we put a minimal amount of logic inside the transfer extrinsic, and instead push most of our logic into a do_transfer internal function.

Remember that things which rely on the #[pallet::*] macros must be in the same file.

But if you look closely, all of the "internal" functions like gen_dna, mint, and soon do_transfer, do not depend on the #[pallet::*] macros at all!

So you could actually move all of this logic into its own file, and that would lead to much cleaner code. The same thing can be said for the definition of the Kitty struct and any other custom types you might use in your Pallet.

However, for the purposes of this tutorial, keeping everything in one file makes things a bit easier to teach.

Your Turn

There is nothing in this step that you are not already familiar with.

Follow the TODOs in the template to:

  • Create a transfer extrinsic.
  • Create a do_transfer internal function.
  • Create a Transferred event.
#![allow(unused)]
fn main() {
use super::*;
use frame::prelude::*;
use frame::primitives::BlakeTwo256;
use frame::traits::Hash;

// Learn about internal functions.
impl<T: Config> Pallet<T> {
	// Generates and returns DNA
	pub fn gen_dna() -> [u8; 32] {
		// Create randomness payload. Multiple kitties can be generated in the same block,
		// retaining uniqueness.
		let unique_payload = (
			frame_system::Pallet::<T>::parent_hash(),
			frame_system::Pallet::<T>::block_number(),
			frame_system::Pallet::<T>::extrinsic_index(),
			CountForKitties::<T>::get(),
		);

		BlakeTwo256::hash_of(&unique_payload).into()
	}

	pub fn mint(owner: T::AccountId, dna: [u8; 32]) -> DispatchResult {
		let kitty = Kitty { dna, owner: owner.clone() };
		// Check if the kitty does not already exist in our storage map
		ensure!(!Kitties::<T>::contains_key(dna), Error::<T>::DuplicateKitty);

		let current_count: u32 = CountForKitties::<T>::get();
		let new_count = current_count.checked_add(1).ok_or(Error::<T>::TooManyKitties)?;

		KittiesOwned::<T>::try_append(&owner, dna).map_err(|_| Error::<T>::TooManyOwned)?;
		Kitties::<T>::insert(dna, kitty);
		CountForKitties::<T>::set(new_count);

		Self::deposit_event(Event::<T>::Created { owner });
		Ok(())
	}

	/* 🚧 TODO 🚧: Create an internal function called `do_transfer`:
		- It has inputs:
			- `from` which is `T::AccountId`.
			- `to` which is `T::AccountId`.
			- `kitty_id` which is `[u8; 32]`.
		- It returns a `DispatchResult`
		- The inner logic for now is:
			- Call `Self::deposit_event` and emit `Event::<T>:Transferred` with params.
			- Return `Ok(())`.
	*/
}
}
#![allow(unused)]
#![cfg_attr(not(feature = "std"), no_std)]

fn main() {
mod impls;
mod tests;

use frame::prelude::*;
pub use pallet::*;

#[frame::pallet(dev_mode)]
pub mod pallet {
	use super::*;

	#[pallet::pallet]
	pub struct Pallet<T>(core::marker::PhantomData<T>);

	#[pallet::config]
	pub trait Config: frame_system::Config {
		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
	}

	#[derive(Encode, Decode, TypeInfo, MaxEncodedLen)]
	#[scale_info(skip_type_params(T))]
	pub struct Kitty<T: Config> {
		// Using 32 bytes to represent a kitty DNA
		pub dna: [u8; 32],
		pub owner: T::AccountId,
	}

	#[pallet::storage]
	pub(super) type CountForKitties<T: Config> = StorageValue<Value = u32, QueryKind = ValueQuery>;

	#[pallet::storage]
	pub(super) type Kitties<T: Config> = StorageMap<Key = [u8; 32], Value = Kitty<T>>;

	/// Track the kitties owned by each account.
	#[pallet::storage]
	pub(super) type KittiesOwned<T: Config> = StorageMap<
		Key = T::AccountId,
		Value = BoundedVec<[u8; 32], ConstU32<100>>,
		QueryKind = ValueQuery,
	>;

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	pub enum Event<T: Config> {
		Created { owner: T::AccountId },
		/* 🚧 TODO 🚧: Create a new event called `Transferred`:
			- Parameters are:
				- `from` which is `T::AccountId`.
				- `to` which is `T::AccountId`.
				- `kitty_id` which is `[u8; 32]`.
		*/
	}

	#[pallet::error]
	pub enum Error<T> {
		TooManyKitties,
		DuplicateKitty,
		TooManyOwned,
	}

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		pub fn create_kitty(origin: OriginFor<T>) -> DispatchResult {
			let who = ensure_signed(origin)?;
			let dna = Self::gen_dna();
			Self::mint(who, dna)?;
			Ok(())
		}

		/* 🚧 TODO 🚧: Make a new extrinsic called `transfer`.
			- Input parameters are:
				- `origin` which is `OriginFor<T>`.
				- `to` which is `T::AccountId`.
				- `kitty_id` which is `[u8; 32]`.
			- Returns a `DispatchResult`.
			- The inner logic should be:
				- Get the caller `who` from `ensure_signed`.
				- Call `Self::do_transfer`, and propagate the result.
				- End with Ok(()).
		*/
	}
}
}
#![allow(unused)]
fn main() {
use super::*;
use frame::prelude::*;
use frame::primitives::BlakeTwo256;
use frame::traits::Hash;

// Learn about internal functions.
impl<T: Config> Pallet<T> {
	// Generates and returns DNA
	pub fn gen_dna() -> [u8; 32] {
		// Create randomness payload. Multiple kitties can be generated in the same block,
		// retaining uniqueness.
		let unique_payload = (
			frame_system::Pallet::<T>::parent_hash(),
			frame_system::Pallet::<T>::block_number(),
			frame_system::Pallet::<T>::extrinsic_index(),
			CountForKitties::<T>::get(),
		);

		BlakeTwo256::hash_of(&unique_payload).into()
	}

	pub fn mint(owner: T::AccountId, dna: [u8; 32]) -> DispatchResult {
		let kitty = Kitty { dna, owner: owner.clone() };
		// Check if the kitty does not already exist in our storage map
		ensure!(!Kitties::<T>::contains_key(dna), Error::<T>::DuplicateKitty);

		let current_count: u32 = CountForKitties::<T>::get();
		let new_count = current_count.checked_add(1).ok_or(Error::<T>::TooManyKitties)?;

		KittiesOwned::<T>::try_append(&owner, dna).map_err(|_| Error::<T>::TooManyOwned)?;
		Kitties::<T>::insert(dna, kitty);
		CountForKitties::<T>::set(new_count);

		Self::deposit_event(Event::<T>::Created { owner });
		Ok(())
	}

	pub fn do_transfer(from: T::AccountId, to: T::AccountId, kitty_id: [u8; 32]) -> DispatchResult {
		Self::deposit_event(Event::<T>::Transferred { from, to, kitty_id });
		Ok(())
	}
}
}
#![allow(unused)]
#![cfg_attr(not(feature = "std"), no_std)]

fn main() {
mod impls;
mod tests;

use frame::prelude::*;
pub use pallet::*;

#[frame::pallet(dev_mode)]
pub mod pallet {
	use super::*;

	#[pallet::pallet]
	pub struct Pallet<T>(core::marker::PhantomData<T>);

	#[pallet::config]
	pub trait Config: frame_system::Config {
		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
	}

	#[derive(Encode, Decode, TypeInfo, MaxEncodedLen)]
	#[scale_info(skip_type_params(T))]
	pub struct Kitty<T: Config> {
		// Using 32 bytes to represent a kitty DNA
		pub dna: [u8; 32],
		pub owner: T::AccountId,
	}

	#[pallet::storage]
	pub(super) type CountForKitties<T: Config> = StorageValue<Value = u32, QueryKind = ValueQuery>;

	#[pallet::storage]
	pub(super) type Kitties<T: Config> = StorageMap<Key = [u8; 32], Value = Kitty<T>>;

	/// Track the kitties owned by each account.
	#[pallet::storage]
	pub(super) type KittiesOwned<T: Config> = StorageMap<
		Key = T::AccountId,
		Value = BoundedVec<[u8; 32], ConstU32<100>>,
		QueryKind = ValueQuery,
	>;

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	pub enum Event<T: Config> {
		Created { owner: T::AccountId },
		Transferred { from: T::AccountId, to: T::AccountId, kitty_id: [u8; 32] },
	}

	#[pallet::error]
	pub enum Error<T> {
		TooManyKitties,
		DuplicateKitty,
		TooManyOwned,
	}

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		pub fn create_kitty(origin: OriginFor<T>) -> DispatchResult {
			let who = ensure_signed(origin)?;
			let dna = Self::gen_dna();
			Self::mint(who, dna)?;
			Ok(())
		}

		pub fn transfer(
			origin: OriginFor<T>,
			to: T::AccountId,
			kitty_id: [u8; 32],
		) -> DispatchResult {
			let who = ensure_signed(origin)?;
			Self::do_transfer(who, to, kitty_id)?;
			Ok(())
		}
	}
}
}
#![allow(unused)]
fn main() {
// Tests for the Kitties Pallet.
//
// Normally this file would be split into two parts: `mock.rs` and `tests.rs`.
// The `mock.rs` file would contain all the setup code for our `TestRuntime`.
// Then `tests.rs` would only have the tests for our pallet.
// However, to minimize the project, these have been combined into this single file.
//
// Learn more about creating tests for Pallets:
// https://paritytech.github.io/polkadot-sdk/master/polkadot_sdk_docs/guides/your_first_pallet/index.html

// This flag tells rust to only run this file when running `cargo test`.
#![cfg(test)]

use crate as pallet_kitties;
use crate::*;
use frame::deps::sp_io;
use frame::runtime::prelude::*;
use frame::testing_prelude::*;
use frame::traits::fungible::*;

type Balance = u64;
type Block = frame_system::mocking::MockBlock<TestRuntime>;

// In our "test runtime", we represent a user `AccountId` with a `u64`.
// This is just a simplification so that we don't need to generate a bunch of proper cryptographic
// public keys when writing tests. It is just easier to say "user 1 transfers to user 2".
// We create the constants `ALICE` and `BOB` to make it clear when we are representing users below.
const ALICE: u64 = 1;
const BOB: u64 = 2;
const DEFAULT_KITTY: Kitty<TestRuntime> = Kitty { dna: [0u8; 32], owner: 0 };

// Our blockchain tests only need 3 Pallets:
// 1. System: Which is included with every FRAME runtime.
// 2. PalletBalances: Which is manages your blockchain's native currency. (i.e. DOT on Polkadot)
// 3. PalletKitties: The pallet you are building in this tutorial!
construct_runtime! {
	pub struct TestRuntime {
		System: frame_system,
		PalletBalances: pallet_balances,
		PalletKitties: pallet_kitties,
	}
}

// Normally `System` would have many more configurations, but you can see that we use some macro
// magic to automatically configure most of the pallet for a "default test configuration".
#[derive_impl(frame_system::config_preludes::TestDefaultConfig)]
impl frame_system::Config for TestRuntime {
	type Block = Block;
	type AccountData = pallet_balances::AccountData<Balance>;
}

// Normally `pallet_balances` would have many more configurations, but you can see that we use some
// macro magic to automatically configure most of the pallet for a "default test configuration".
#[derive_impl(pallet_balances::config_preludes::TestDefaultConfig)]
impl pallet_balances::Config for TestRuntime {
	type AccountStore = System;
	type Balance = Balance;
}

// This is the configuration of our Pallet! If you make changes to the pallet's `trait Config`, you
// will also need to update this configuration to represent that.
impl pallet_kitties::Config for TestRuntime {
	type RuntimeEvent = RuntimeEvent;
}

// We need to run most of our tests using this function: `new_test_ext().execute_with(|| { ... });`
// It simulates the blockchain database backend for our tests.
// If you forget to include this and try to access your Pallet storage, you will get an error like:
// "`get_version_1` called outside of an Externalities-provided environment."
pub fn new_test_ext() -> sp_io::TestExternalities {
	frame_system::GenesisConfig::<TestRuntime>::default()
		.build_storage()
		.unwrap()
		.into()
}

#[test]
fn starting_template_is_sane() {
	new_test_ext().execute_with(|| {
		let event = Event::<TestRuntime>::Created { owner: ALICE };
		let _runtime_event: RuntimeEvent = event.into();
		let _call = Call::<TestRuntime>::create_kitty {};
		let result = PalletKitties::create_kitty(RuntimeOrigin::signed(BOB));
		assert_ok!(result);
	});
}

#[test]
fn system_and_balances_work() {
	// This test will just sanity check that we can access `System` and `PalletBalances`.
	new_test_ext().execute_with(|| {
		// We often need to set `System` to block 1 so that we can see events.
		System::set_block_number(1);
		// We often need to add some balance to a user to test features which needs tokens.
		assert_ok!(PalletBalances::mint_into(&ALICE, 100));
		assert_ok!(PalletBalances::mint_into(&BOB, 100));
	});
}

#[test]
fn create_kitty_checks_signed() {
	new_test_ext().execute_with(|| {
		// The `create_kitty` extrinsic should work when being called by a user.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// The `create_kitty` extrinsic should fail when being called by an unsigned message.
		assert_noop!(PalletKitties::create_kitty(RuntimeOrigin::none()), DispatchError::BadOrigin);
	})
}

#[test]
fn create_kitty_emits_event() {
	new_test_ext().execute_with(|| {
		// We need to set block number to 1 to view events.
		System::set_block_number(1);
		// Execute our call, and ensure it is successful.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// Assert the last event by our blockchain is the `Created` event with the correct owner.
		System::assert_last_event(Event::<TestRuntime>::Created { owner: 1 }.into());
	})
}

#[test]
fn count_for_kitties_created_correctly() {
	new_test_ext().execute_with(|| {
		// Querying storage before anything is set will return `0`.
		assert_eq!(CountForKitties::<TestRuntime>::get(), 0);
		// You can `set` the value using an `u32`.
		CountForKitties::<TestRuntime>::set(1337u32);
		// You can `put` the value directly with a `u32`.
		CountForKitties::<TestRuntime>::put(1337u32);
	})
}

#[test]
fn mint_increments_count_for_kitty() {
	new_test_ext().execute_with(|| {
		// Querying storage before anything is set will return `0`.
		assert_eq!(CountForKitties::<TestRuntime>::get(), 0);
		// Call `create_kitty` which will call `mint`.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// Now the storage should be `1`
		assert_eq!(CountForKitties::<TestRuntime>::get(), 1);
	})
}

#[test]
fn mint_errors_when_overflow() {
	new_test_ext().execute_with(|| {
		// Set the count to the largest value possible.
		CountForKitties::<TestRuntime>::set(u32::MAX);
		// `create_kitty` should not succeed because of safe math.
		assert_noop!(
			PalletKitties::create_kitty(RuntimeOrigin::signed(1)),
			Error::<TestRuntime>::TooManyKitties
		);
	})
}

#[test]
fn kitties_map_created_correctly() {
	new_test_ext().execute_with(|| {
		let zero_key = [0u8; 32];
		assert!(!Kitties::<TestRuntime>::contains_key(zero_key));
		Kitties::<TestRuntime>::insert(zero_key, DEFAULT_KITTY);
		assert!(Kitties::<TestRuntime>::contains_key(zero_key));
	})
}

#[test]
fn create_kitty_adds_to_map() {
	new_test_ext().execute_with(|| {
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		assert_eq!(Kitties::<TestRuntime>::iter().count(), 1);
	})
}

#[test]
fn cannot_mint_duplicate_kitty() {
	new_test_ext().execute_with(|| {
		assert_ok!(PalletKitties::mint(ALICE, [0u8; 32]));
		assert_noop!(PalletKitties::mint(BOB, [0u8; 32]), Error::<TestRuntime>::DuplicateKitty);
	})
}

#[test]
fn kitty_struct_has_expected_traits() {
	new_test_ext().execute_with(|| {
		let kitty = DEFAULT_KITTY;
		let bytes = kitty.encode();
		let _decoded_kitty = Kitty::<TestRuntime>::decode(&mut &bytes[..]).unwrap();
		assert!(Kitty::<TestRuntime>::max_encoded_len() > 0);
		let _info = Kitty::<TestRuntime>::type_info();
	})
}

#[test]
fn mint_stores_owner_in_kitty() {
	new_test_ext().execute_with(|| {
		assert_ok!(PalletKitties::mint(1337, [42u8; 32]));
		let kitty = Kitties::<TestRuntime>::get([42u8; 32]).unwrap();
		assert_eq!(kitty.owner, 1337);
		assert_eq!(kitty.dna, [42u8; 32]);
	})
}

#[test]
fn create_kitty_makes_unique_kitties() {
	new_test_ext().execute_with(|| {
		// Two calls to `create_kitty` should work.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(BOB)));
		// And should result in two kitties in our system.
		assert_eq!(CountForKitties::<TestRuntime>::get(), 2);
		assert_eq!(Kitties::<TestRuntime>::iter().count(), 2);
	})
}

#[test]
fn kitties_owned_created_correctly() {
	new_test_ext().execute_with(|| {
		// Initially users have no kitties owned.
		assert_eq!(KittiesOwned::<TestRuntime>::get(1).len(), 0);
		// Let's create two kitties.
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// Now they should have two kitties owned.
		assert_eq!(KittiesOwned::<TestRuntime>::get(1).len(), 2);
	});
}

#[test]
fn cannot_own_too_many_kitties() {
	new_test_ext().execute_with(|| {
		// If your max owned is different than 100, you will need to update this.
		for _ in 0..100 {
			assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		}
		assert_noop!(
			PalletKitties::create_kitty(RuntimeOrigin::signed(1)),
			Error::<TestRuntime>::TooManyOwned
		);
	});
}

#[test]
fn transfer_emits_event() {
	new_test_ext().execute_with(|| {
		// We need to set block number to 1 to view events.
		System::set_block_number(1);
		// Create a kitty to transfer
		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
		// Get the kitty id.
		let kitty_id = Kitties::<TestRuntime>::iter_keys().collect::<Vec<_>>()[0];
		assert_ok!(PalletKitties::transfer(RuntimeOrigin::signed(ALICE), BOB, kitty_id));
		System::assert_last_event(
			Event::<TestRuntime>::Transferred { from: ALICE, to: BOB, kitty_id }.into(),
		);
	});
}
}
diff --git a/src/impls.rs b/src/impls.rs
index 793dec3..3dd1565 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -34,4 +34,15 @@ impl<T: Config> Pallet<T> {
 		Self::deposit_event(Event::<T>::Created { owner });
 		Ok(())
 	}
+
+	/* 🚧 TODO 🚧: Create an internal function called `do_transfer`:
+		- It has inputs:
+			- `from` which is `T::AccountId`.
+			- `to` which is `T::AccountId`.
+			- `kitty_id` which is `[u8; 32]`.
+		- It returns a `DispatchResult`
+		- The inner logic for now is:
+			- Call `Self::deposit_event` and emit `Event::<T>:Transferred` with params.
+			- Return `Ok(())`.
+	*/
 }
diff --git a/src/lib.rs b/src/lib.rs
index e032974..ac84fa6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -44,6 +44,12 @@ pub mod pallet {
 	#[pallet::generate_deposit(pub(super) fn deposit_event)]
 	pub enum Event<T: Config> {
 		Created { owner: T::AccountId },
+		/* 🚧 TODO 🚧: Create a new event called `Transferred`:
+			- Parameters are:
+				- `from` which is `T::AccountId`.
+				- `to` which is `T::AccountId`.
+				- `kitty_id` which is `[u8; 32]`.
+		*/
 	}
 
 	#[pallet::error]
@@ -61,5 +67,17 @@ pub mod pallet {
 			Self::mint(who, dna)?;
 			Ok(())
 		}
+
+		/* 🚧 TODO 🚧: Make a new extrinsic called `transfer`.
+			- Input parameters are:
+				- `origin` which is `OriginFor<T>`.
+				- `to` which is `T::AccountId`.
+				- `kitty_id` which is `[u8; 32]`.
+			- Returns a `DispatchResult`.
+			- The inner logic should be:
+				- Get the caller `who` from `ensure_signed`.
+				- Call `Self::do_transfer`, and propagate the result.
+				- End with Ok(()).
+		*/
 	}
 }
diff --git a/src/impls.rs b/src/impls.rs
index 3dd1565..9d435f5 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -35,14 +35,8 @@ impl<T: Config> Pallet<T> {
 		Ok(())
 	}
 
-	/* 🚧 TODO 🚧: Create an internal function called `do_transfer`:
-		- It has inputs:
-			- `from` which is `T::AccountId`.
-			- `to` which is `T::AccountId`.
-			- `kitty_id` which is `[u8; 32]`.
-		- It returns a `DispatchResult`
-		- The inner logic for now is:
-			- Call `Self::deposit_event` and emit `Event::<T>:Transferred` with params.
-			- Return `Ok(())`.
-	*/
+	pub fn do_transfer(from: T::AccountId, to: T::AccountId, kitty_id: [u8; 32]) -> DispatchResult {
+		Self::deposit_event(Event::<T>::Transferred { from, to, kitty_id });
+		Ok(())
+	}
 }
diff --git a/src/lib.rs b/src/lib.rs
index ac84fa6..971af78 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -44,12 +44,7 @@ pub mod pallet {
 	#[pallet::generate_deposit(pub(super) fn deposit_event)]
 	pub enum Event<T: Config> {
 		Created { owner: T::AccountId },
-		/* 🚧 TODO 🚧: Create a new event called `Transferred`:
-			- Parameters are:
-				- `from` which is `T::AccountId`.
-				- `to` which is `T::AccountId`.
-				- `kitty_id` which is `[u8; 32]`.
-		*/
+		Transferred { from: T::AccountId, to: T::AccountId, kitty_id: [u8; 32] },
 	}
 
 	#[pallet::error]
@@ -68,16 +63,14 @@ pub mod pallet {
 			Ok(())
 		}
 
-		/* 🚧 TODO 🚧: Make a new extrinsic called `transfer`.
-			- Input parameters are:
-				- `origin` which is `OriginFor<T>`.
-				- `to` which is `T::AccountId`.
-				- `kitty_id` which is `[u8; 32]`.
-			- Returns a `DispatchResult`.
-			- The inner logic should be:
-				- Get the caller `who` from `ensure_signed`.
-				- Call `Self::do_transfer`, and propagate the result.
-				- End with Ok(()).
-		*/
+		pub fn transfer(
+			origin: OriginFor<T>,
+			to: T::AccountId,
+			kitty_id: [u8; 32],
+		) -> DispatchResult {
+			let who = ensure_signed(origin)?;
+			Self::do_transfer(who, to, kitty_id)?;
+			Ok(())
+		}
 	}
 }
diff --git a/src/tests.rs b/src/tests.rs
index 98a5ade..9a1878d 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -241,3 +241,19 @@ fn cannot_own_too_many_kitties() {
 		);
 	});
 }
+
+#[test]
+fn transfer_emits_event() {
+	new_test_ext().execute_with(|| {
+		// We need to set block number to 1 to view events.
+		System::set_block_number(1);
+		// Create a kitty to transfer
+		assert_ok!(PalletKitties::create_kitty(RuntimeOrigin::signed(ALICE)));
+		// Get the kitty id.
+		let kitty_id = Kitties::<TestRuntime>::iter_keys().collect::<Vec<_>>()[0];
+		assert_ok!(PalletKitties::transfer(RuntimeOrigin::signed(ALICE), BOB, kitty_id));
+		System::assert_last_event(
+			Event::<TestRuntime>::Transferred { from: ALICE, to: BOB, kitty_id }.into(),
+		);
+	});
+}