Basic Balance Test

Now that we have the basics of our Pallet set up, let's actually interact with it.

For that, we will go back to the main.rs file, and create our first #[test] which will play with the code we have written so far.

  1. In your src/balances.rs file, add a new #[test] named fn init_balances():

    #![allow(unused)]
fn main() {
#[test]
fn init_balances() { }
}

  2. To begin our test, we need to initialize a new instance of our Pallet:

    #![allow(unused)]
fn main() {
#[test]
fn init_balances() {
	let mut balances = super::Pallet::new();
}
}

    Note that we make this variable mut since we plan to mutate our state using our newly created API.

  3. Finally, let's check that our read and write APIs are working as expected:

    #![allow(unused)]
fn main() {
#[test]
fn init_balances() {
	let mut balances = super::Pallet::new();

	assert_eq!(balances.balance(&"alice".to_string()), 0);
	balances.set_balance(&"alice".to_string(), 100);
	assert_eq!(balances.balance(&"alice".to_string()), 100);
	assert_eq!(balances.balance(&"bob".to_string()), 0);
}
}

  4. We can run our tests using cargo test, where hopefully you should see that it passes. There should be no compiler warnings now!

I hope at this point you can start to see the beginnings of your simple blockchain state machine.

#![allow(unused)]
fn main() {
use std::collections::BTreeMap;

/// This is the Balances Module.
/// It is a simple module which keeps track of how much balance each account has in this state
/// machine.
pub struct Pallet {
	// A simple storage mapping from accounts (`String`) to their balances (`u128`).
	balances: BTreeMap<String, u128>,
}

impl Pallet {
	/// Create a new instance of the balances module.
	pub fn new() -> Self {
		Self { balances: BTreeMap::new() }
	}

	/// Set the balance of an account `who` to some `amount`.
	pub fn set_balance(&mut self, who: &String, amount: u128) {
		self.balances.insert(who.clone(), amount);
	}

	/// Get the balance of an account `who`.
	/// If the account has no stored balance, we return zero.
	pub fn balance(&self, who: &String) -> u128 {
		*self.balances.get(who).unwrap_or(&0)
	}
}

#[cfg(test)]
mod tests {
	#[test]
	fn init_balances() {
		/* TODO: Create a mutable variable `balances`, which is a new instance of `Pallet`. */

		/* TODO: Assert that the balance of `alice` starts at zero. */
		/* TODO: Set the balance of `alice` to 100. */
		/* TODO: Assert the balance of `alice` is now 100. */
		/* TODO: Assert the balance of `bob` has not changed and is 0. */
	}
}
}
#![allow(unused)]
fn main() {
use std::collections::BTreeMap;

/// This is the Balances Module.
/// It is a simple module which keeps track of how much balance each account has in this state
/// machine.
pub struct Pallet {
	// A simple storage mapping from accounts (`String`) to their balances (`u128`).
	balances: BTreeMap<String, u128>,
}

impl Pallet {
	/// Create a new instance of the balances module.
	pub fn new() -> Self {
		Self { balances: BTreeMap::new() }
	}

	/// Set the balance of an account `who` to some `amount`.
	pub fn set_balance(&mut self, who: &String, amount: u128) {
		self.balances.insert(who.clone(), amount);
	}

	/// Get the balance of an account `who`.
	/// If the account has no stored balance, we return zero.
	pub fn balance(&self, who: &String) -> u128 {
		*self.balances.get(who).unwrap_or(&0)
	}
}

#[cfg(test)]
mod tests {
	#[test]
	fn init_balances() {
		let mut balances = super::Pallet::new();

		assert_eq!(balances.balance(&"alice".to_string()), 0);
		balances.set_balance(&"alice".to_string(), 100);
		assert_eq!(balances.balance(&"alice".to_string()), 100);
		assert_eq!(balances.balance(&"bob".to_string()), 0);
	}
}
}
diff --git a/src/balances.rs b/src/balances.rs
index 2a6bbfbc..788d61c1 100644
--- a/src/balances.rs
+++ b/src/balances.rs
@@ -25,3 +25,16 @@ impl Pallet {
 		*self.balances.get(who).unwrap_or(&0)
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	#[test]
+	fn init_balances() {
+		/* TODO: Create a mutable variable `balances`, which is a new instance of `Pallet`. */
+
+		/* TODO: Assert that the balance of `alice` starts at zero. */
+		/* TODO: Set the balance of `alice` to 100. */
+		/* TODO: Assert the balance of `alice` is now 100. */
+		/* TODO: Assert the balance of `bob` has not changed and is 0. */
+	}
+}

diff --git a/src/balances.rs b/src/balances.rs
index 788d61c1..ea4e0424 100644
--- a/src/balances.rs
+++ b/src/balances.rs
@@ -30,11 +30,11 @@ impl Pallet {
 mod tests {
 	#[test]
 	fn init_balances() {
-		/* TODO: Create a mutable variable `balances`, which is a new instance of `Pallet`. */
+		let mut balances = super::Pallet::new();
 
-		/* TODO: Assert that the balance of `alice` starts at zero. */
-		/* TODO: Set the balance of `alice` to 100. */
-		/* TODO: Assert the balance of `alice` is now 100. */
-		/* TODO: Assert the balance of `bob` has not changed and is 0. */
+		assert_eq!(balances.balance(&"alice".to_string()), 0);
+		balances.set_balance(&"alice".to_string(), 100);
+		assert_eq!(balances.balance(&"alice".to_string()), 100);
+		assert_eq!(balances.balance(&"bob".to_string()), 0);
 	}
 }