From 9b61d89fc4f482c04321e622b3e255724d265bab Mon Sep 17 00:00:00 2001
From: laentropia <aadrian887mh@gmail.com>
Date: Wed, 29 Apr 2026 17:34:26 -0600
Subject: [PATCH] test: tests for mult

---
 src/lib.rs | 190 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 189 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 4288d87..554f8bb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -522,7 +522,7 @@ impl Mul for Matrix {
                 let current_column = other.get_column(k)?;
                 let current_row = self.get_row(i)?;
 
-                let mut new_value = Fraction::new(0, 1).unwrap();
+                let mut new_value = Fraction::from(0);
 
                 for (a, b) in current_row.zip(current_column) {
                     new_value = new_value + (*a * *b);
@@ -3397,4 +3397,192 @@ mod tests {
 
         assert_eq!(result.data, expected);
     }
+
+    #[test]
+    fn test_mul_basic_2x2() {
+        let a = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(1),
+                Fraction::from(2),
+                Fraction::from(3),
+                Fraction::from(4),
+            ],
+        };
+
+        let b = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(5),
+                Fraction::from(6),
+                Fraction::from(7),
+                Fraction::from(8),
+            ],
+        };
+
+        let result = (a * b).unwrap();
+
+        let expected = vec![
+            Fraction::from(19),
+            Fraction::from(22),
+            Fraction::from(43),
+            Fraction::from(50),
+        ];
+
+        assert_eq!(result.data, expected);
+    }
+
+    #[test]
+    fn test_mul_identity() {
+        let a = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(3),
+                Fraction::from(4),
+                Fraction::from(5),
+                Fraction::from(6),
+            ],
+        };
+
+        let identity = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(1),
+                Fraction::from(0),
+                Fraction::from(0),
+                Fraction::from(1),
+            ],
+        };
+
+        let result = (a.clone() * identity).unwrap();
+
+        assert_eq!(result.data, a.data);
+    }
+
+    #[test]
+    fn test_mul_not_commutative() {
+        let a = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(1),
+                Fraction::from(2),
+                Fraction::from(3),
+                Fraction::from(4),
+            ],
+        };
+
+        let b = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(2),
+                Fraction::from(0),
+                Fraction::from(1),
+                Fraction::from(2),
+            ],
+        };
+
+        let res1 = (a.clone() * b.clone()).unwrap();
+        let res2 = (b * a).unwrap();
+
+        assert_ne!(res1.data, res2.data);
+    }
+
+    #[test]
+    fn test_mul_rectangular() {
+        // 2x3 * 3x2
+        let a = Matrix {
+            rows: 2,
+            columns: 3,
+            data: vec![
+                Fraction::from(1),
+                Fraction::from(2),
+                Fraction::from(3),
+                Fraction::from(4),
+                Fraction::from(5),
+                Fraction::from(6),
+            ],
+        };
+
+        let b = Matrix {
+            rows: 3,
+            columns: 2,
+            data: vec![
+                Fraction::from(7),
+                Fraction::from(8),
+                Fraction::from(9),
+                Fraction::from(10),
+                Fraction::from(11),
+                Fraction::from(12),
+            ],
+        };
+
+        let result = (a * b).unwrap();
+
+        let expected = vec![
+            Fraction::from(58),
+            Fraction::from(64),
+            Fraction::from(139),
+            Fraction::from(154),
+        ];
+
+        assert_eq!(result.data, expected);
+    }
+
+    #[test]
+    fn test_mul_invalid_size() {
+        let a = Matrix::new(2, 3, Fraction::from(1)).unwrap();
+        let b = Matrix::new(2, 2, Fraction::from(1)).unwrap();
+
+        let result = a * b;
+
+        assert!(matches!(result, Err(MatrixError::InvalidSizeForMul)));
+    }
+
+    #[test]
+    fn test_mul_zero_matrix() {
+        let a = Matrix::new(2, 2, Fraction::from(5)).unwrap();
+        let zero = Matrix::new(2, 2, Fraction::from(0)).unwrap();
+
+        let result = (a * zero).unwrap();
+
+        assert!(result.data.iter().all(|x| x.is_zero()));
+    }
+
+    #[test]
+    fn test_mul_fractions() {
+        let a = Matrix {
+            rows: 1,
+            columns: 2,
+            data: vec![Fraction::new(1, 2).unwrap(), Fraction::new(1, 3).unwrap()],
+        };
+
+        let b = Matrix {
+            rows: 2,
+            columns: 1,
+            data: vec![Fraction::new(2, 1).unwrap(), Fraction::new(3, 1).unwrap()],
+        };
+
+        let result = (a * b).unwrap();
+
+        // (1/2 * 2) + (1/3 * 3) = 1 + 1 = 2
+        assert_eq!(result.data, vec![Fraction::from(2)]);
+    }
+
+    #[test]
+    fn test_mul_associative() {
+        let a = Matrix::new(2, 2, Fraction::from(1)).unwrap();
+        let b = Matrix::new(2, 2, Fraction::from(2)).unwrap();
+        let c = Matrix::new(2, 2, Fraction::from(3)).unwrap();
+
+        let res1 = ((a.clone() * b.clone()).unwrap() * c.clone()).unwrap();
+        let res2 = (a * (b * c).unwrap()).unwrap();
+
+        assert_eq!(res1.data, res2.data);
+    }
 }