test: substraction

src/lib.rs

@@ -136,7 +136,7 @@ impl ops::Sub for Fraction {
     fn sub(self, other: Self) -> Self::Output {
         let mut new = Fraction {
             num: (self.num * other.den) - (self.den * other.num),
-            den: self.num * other.den,
+            den: self.den * other.den,
         };
         new.reduce();
         new.correct_sign();
@@ -293,4 +293,58 @@ mod tests {
         assert_eq!(c.num, 4);
         assert_eq!(c.den, 7);
     }
+
+    #[test]
+    fn test_sub_basic() {
+        let a = Fraction::new(7, 13).unwrap();
+        let b = Fraction::new(4, 7).unwrap();
+        let c = a - b;
+        assert_eq!(c.num, -3);
+        assert_eq!(c.den, 91);
+    }
+
+    #[test]
+    fn test_sub_with_common_denominator() {
+        let a = Fraction::new(7, 13).unwrap();
+        let b = Fraction::new(4, 13).unwrap();
+        let c = a - b;
+        assert_eq!(c.num, 3);
+        assert_eq!(c.den, 13);
+    }
+
+    #[test]
+    fn test_sub_positive_and_negative() {
+        let a = Fraction::new(-32, 237).unwrap();
+        let b = Fraction::new(22, 44).unwrap();
+        let c = a - b;
+        assert_eq!(c.num, -301);
+        assert_eq!(c.den, 474);
+    }
+
+    #[test]
+    fn test_sub_negative_and_negative() {
+        let a = Fraction::new(-500, 12).unwrap();
+        let b = Fraction::new(-22, 4).unwrap();
+        let c = a - b;
+        assert_eq!(c.num, -217);
+        assert_eq!(c.den, 6);
+    }
+
+    #[test]
+    fn test_sub_with_zero() {
+        let a = Fraction::new(0, 13).unwrap();
+        let b = Fraction::new(4, 7).unwrap();
+        let c = a - b;
+        assert_eq!(c.num, -4);
+        assert_eq!(c.den, 7);
+    }
+
+    #[test]
+    fn test_sub_result_zero() {
+        let a = Fraction::new(5, 9).unwrap();
+        let b = Fraction::new(5, 9).unwrap();
+        let c = a - b;
+        assert_eq!(c.num, 0);
+        assert_eq!(c.den, 1);
+    }
 }