test: new

src/lib.rs

@@ -1,11 +1,12 @@
 use std::{fmt, ops};
 
+#[derive(Debug, PartialEq, Eq)]
 pub struct Fraction {
     num: i64,
     den: i64,
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq, Eq)]
 pub enum FractionError {
     DivisionByZero,
     ZeroDenominator,
@@ -220,4 +221,31 @@ impl TryInto<i64> for Fraction {
 #[cfg(test)]
 mod tests {
     use super::*;
+
+    #[test]
+    fn test_new_valid_fraction() {
+        let f = Fraction::new(2, 4).unwrap();
+        assert_eq!(f.num, 1);
+        assert_eq!(f.den, 2);
+    }
+
+    #[test]
+    fn test_new_zero_denominator_error() {
+        let f = Fraction::new(2, 0);
+        assert!(matches!(f, Err(FractionError::ZeroDenominator)));
+    }
+
+    #[test]
+    fn test_new_reduces_fraction() {
+        let f = Fraction::new(256, 512).unwrap();
+        assert_eq!(f.num, 1);
+        assert_eq!(f.den, 2);
+    }
+
+    #[test]
+    fn test_new_normalizes_signs() {
+        let f = Fraction::new(1, -2).unwrap();
+        assert_eq!(f.num, -1);
+        assert_eq!(f.den, 2);
+    }
 }