From 5ff1370d318d713d0a22820eca6dafbaf5f5aec6 Mon Sep 17 00:00:00 2001
From: laentropia <aadrian887mh@gmail.com>
Date: Wed, 29 Apr 2026 17:23:31 -0600
Subject: [PATCH] test: solve with inverse

---
 src/lib.rs | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 151 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index dd98891..4996191 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -444,17 +444,23 @@ impl Matrix {
 
     pub fn solve_matrix_with_inverse(
         &self,
-        solution_matrix: Matrix,
+        solution_matrix: Vec<Fraction>,
     ) -> Result<Matrix, MatrixError> {
         if self.columns != self.rows {
             return Err(MatrixError::NotSquared);
         }
 
-        if solution_matrix.rows != self.rows || solution_matrix.columns != 1 {
+        if solution_matrix.len() != self.rows {
             return Err(MatrixError::InvalidDataSize);
         }
 
-        let solution_matrix = (self.inverse()? * solution_matrix)?;
+        let sol = Matrix {
+            rows: self.rows,
+            columns: 1,
+            data: solution_matrix,
+        };
+
+        let solution_matrix = (self.inverse()? * sol)?;
 
         Ok(solution_matrix)
     }
@@ -2962,4 +2968,146 @@ mod tests {
 
         assert!(matches!(res, Err(MatrixError::NotSquared)));
     }
+
+    #[test]
+    fn test_solve_inverse_simple() {
+        // 2x + y = 5
+        // x + y = 3
+        let m = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(2),
+                Fraction::from(1),
+                Fraction::from(1),
+                Fraction::from(1),
+            ],
+        };
+
+        let b = vec![Fraction::from(5), Fraction::from(3)];
+
+        let res = m.solve_matrix_with_inverse(b).unwrap();
+
+        let expected = vec![Fraction::from(2), Fraction::from(1)];
+
+        for i in 0..2 {
+            assert_eq!(*res.get(i, 0).unwrap(), expected[i]);
+        }
+    }
+
+    #[test]
+    fn test_solve_inverse_3x3() {
+        let m = Matrix {
+            rows: 3,
+            columns: 3,
+            data: vec![
+                Fraction::from(2),
+                Fraction::from(1),
+                Fraction::from(-1),
+                Fraction::from(-3),
+                Fraction::from(-1),
+                Fraction::from(2),
+                Fraction::from(-2),
+                Fraction::from(1),
+                Fraction::from(2),
+            ],
+        };
+
+        let b = vec![Fraction::from(8), Fraction::from(-11), Fraction::from(-3)];
+
+        let res = m.solve_matrix_with_inverse(b).unwrap();
+
+        let expected = vec![Fraction::from(2), Fraction::from(3), Fraction::from(-1)];
+
+        for i in 0..3 {
+            assert_eq!(*res.get(i, 0).unwrap(), expected[i]);
+        }
+    }
+
+    #[test]
+    fn test_solve_inverse_identity() {
+        let m = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(1),
+                Fraction::from(0),
+                Fraction::from(0),
+                Fraction::from(1),
+            ],
+        };
+
+        let b = vec![Fraction::from(7), Fraction::from(9)];
+
+        let res = m.solve_matrix_with_inverse(b.clone()).unwrap();
+
+        for i in 0..2 {
+            assert_eq!(*res.get(i, 0).unwrap(), b[i]);
+        }
+    }
+
+    #[test]
+    fn test_solve_inverse_singular() {
+        let m = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(1),
+                Fraction::from(2),
+                Fraction::from(2),
+                Fraction::from(4),
+            ],
+        };
+
+        let b = vec![Fraction::from(3), Fraction::from(6)];
+
+        let res = m.solve_matrix_with_inverse(b);
+
+        assert!(matches!(res, Err(MatrixError::FailedGaussJordan)));
+    }
+
+    #[test]
+    fn test_solve_inverse_invalid_size() {
+        let m = Matrix::new(2, 2, Fraction::from(1)).unwrap();
+
+        let b = vec![Fraction::from(1)];
+
+        let res = m.solve_matrix_with_inverse(b);
+
+        assert!(matches!(res, Err(MatrixError::InvalidDataSize)));
+    }
+
+    #[test]
+    fn test_solve_inverse_not_squared() {
+        let m = Matrix::new(2, 3, Fraction::from(1)).unwrap();
+
+        let b = vec![Fraction::from(1), Fraction::from(2)];
+
+        let res = m.solve_matrix_with_inverse(b);
+
+        assert!(matches!(res, Err(MatrixError::NotSquared)));
+    }
+
+    #[test]
+    fn test_solve_inverse_vs_gauss_jordan() {
+        let m = Matrix {
+            rows: 2,
+            columns: 2,
+            data: vec![
+                Fraction::from(3),
+                Fraction::from(2),
+                Fraction::from(1),
+                Fraction::from(2),
+            ],
+        };
+
+        let b = vec![Fraction::from(5), Fraction::from(5)];
+
+        let res_inv = m.solve_matrix_with_inverse(b.clone()).unwrap();
+        let res_gj = m.solve_matrix_with_gauss_jordan(b).unwrap();
+
+        for i in 0..2 {
+            assert_eq!(*res_inv.get(i, 0).unwrap(), res_gj[i]);
+        }
+    }
 }