Add the subject and test of the exercise `traits`

rust/tests/traits_test/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "traits"
+version = "0.1.0"
+
+[[package]]
+name = "traits_test"
+version = "0.1.0"
+dependencies = [
+ "traits",
+]

rust/tests/traits_test/Cargo.toml

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+[package]
+name = "traits_test"
+version = "0.1.0"
+authors = ["Augusto <aug.ornelas@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+traits = { path = "../../../../rust-piscine-solutions/traits"}

rust/tests/traits_test/src/main.rs

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+// Imagine you are designing a new video game and you have to create
+// food that they players can take to gain strength there are two
+// types of food for now fruits and meet: fruits increases the
+// strengths by 1 unit and meat increases it by 3 unit.
+
+// Define both structures fruits and meat
+// Define the std::fmt::Display trait of the Player structure so using
+// the template {} inside a println! macro will print in the first
+// line the name of the player
+// in the second line the strength, score and the money
+// and in the third line the weapons
+use traits::{Food, Fruit, Meat, Player};
+
+fn main() {
+	let apple = Fruit { weight_in_kg: 1.0 };
+	assert_eq!(apple.gives(), 4);
+	let steak = Meat {
+		weight_in_kg: 1.0,
+		fat_content: 1.0,
+	};
+
+	let mut player1 = Player {
+		name: String::from("player1"),
+		strength: 1,
+		score: 0,
+		money: 0,
+		weapons: vec![String::from("knife")],
+	};
+	println!("Before eating {:?}", player1);
+	player1.eat(apple);
+	println!("After eating an apple\n{:?}", player1);
+	player1.eat(steak);
+	println!("After eating a steak\n{:?}", player1);
+}
+
+#[test]
+fn test_gives() {
+	let apple = Fruit { weight_in_kg: 1.0 };
+	assert_eq!(apple.gives(), 4);
+	let steak = Meat {
+		weight_in_kg: 1.0,
+		fat_content: 1.0,
+	};
+	assert_eq!(steak.gives(), 9);
+}
+
+#[test]
+fn test_eat() {
+	let apple = Fruit { weight_in_kg: 1.0 };
+	assert_eq!(apple.gives(), 4);
+	let steak = Meat {
+		weight_in_kg: 1.0,
+		fat_content: 1.0,
+	};
+
+	let mut player1 = Player {
+		name: String::from("player1"),
+		strength: 1,
+		score: 0,
+		money: 0,
+		weapons: vec![String::from("knife")],
+	};
+	player1.eat(apple);
+	assert_eq!(player1.strength, 5);
+	player1.eat(steak);
+	assert_eq!(player1.strength, 14);
+}

subjects/traits/README.md

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+## traits
+
+### Instructions
+
+Imagine you are designing a new video game and you have to create food that they players can take to gain strength. 
+
+There are two types of food for now fruits and meet: fruits increases the strengths by 1 unit and meat increases it by 3 unit.
+
+- Define both structures fruits and meat:
+
+Define the std::fmt::Display trait of the Player structure so using the template {} inside a println! macro will print:
+
+- In the first line the name of the player
+- In the second line the strength, score and the money
+- In the third line the weapons
+
+### Expected Functions and Structures
+
+```rust
+#[derive(Debug)]
+pub struct Player {
+	pub name: String,
+	pub strength: u32,
+	pub score: i32,
+	pub money: i32,
+	pub weapons: Vec<String>,
+}
+
+pub struct Fruit {
+	pub weight_in_kg: f64,
+}
+
+pub struct Meat {
+	pub weight_in_kg: f64,
+	pub fat_content: f64,
+}
+
+impl Player {
+	fn eat(&mut self, food: T) {
+		self.strength += food.gives();
+	}
+}
+
+pub trait Food {
+	fn gives(&self) -> u32;
+}
+
+impl Food for Fruit {
+}
+
+impl Food for Meat {
+}
+```
+
+### Usage
+
+Here is a program to test your function.
+
+```rust
+fn main() {
+	let apple = Fruit { weight_in_kg: 1.0 };
+	assert_eq!(apple.gives(), 4);
+	let steak = Meat {
+		weight_in_kg: 1.0,
+		fat_content: 1.0,
+	};
+
+	let mut player1 = Player {
+		name: String::from("player1"),
+		strength: 1,
+		score: 0,
+		money: 0,
+		weapons: vec![String::from("knife")],
+	};
+	println!("Before eating {:?}", player1);
+	player1.eat(apple);
+	println!("After eating an apple\n{:?}", player1);
+	player1.eat(steak);
+	println!("After eating a steak\n{:?}", player1);
+}
+```
+
+And its output
+
+```console
+student@ubuntu:~/[[ROOT]]/test$ cargo run
+Before eating Player { name: "player1", strength: 1, score: 0, money: 0, weapons: ["knife"] }
+After eating an apple
+Player { name: "player1", strength: 5, score: 0, money: 0, weapons: ["knife"] }
+After eating a steak
+Player { name: "player1", strength: 14, score: 0, money: 0, weapons: ["knife"] }
+student@ubuntu:~/[[ROOT]]/test$
+```