From dc4d0c8e731053b920f37e1691dd2fb6bc7608a9 Mon Sep 17 00:00:00 2001
From: laentropia <aadrian887mh@gmail.com>
Date: Wed, 29 Apr 2026 17:18:35 -0600
Subject: [PATCH] test: solve with gauss jordan

---
 src/lib.rs | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 113 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index b005e4b..dd98891 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -435,7 +435,7 @@ impl Matrix {
         let solved_matrix = solved_matrix.gauss_jordan_elimination()?;
 
         let result = solved_matrix
-            .get_column(solved_matrix.columns)?
+            .get_column(solved_matrix.columns - 1)?
             .cloned()
             .collect();
 
@@ -2850,4 +2850,116 @@ mod tests {
 
         assert!(matches!(res, Err(MatrixError::NotSquared)));
     }
+
+    #[test]
+    fn test_solve_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_gauss_jordan(b).unwrap();
+
+        assert_eq!(res, vec![Fraction::from(2), Fraction::from(1)]);
+    }
+
+    #[test]
+    fn test_solve_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_gauss_jordan(b).unwrap();
+
+        assert_eq!(
+            res,
+            vec![Fraction::from(2), Fraction::from(3), Fraction::from(-1)]
+        );
+    }
+
+    #[test]
+    fn test_solve_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_gauss_jordan(b.clone()).unwrap();
+
+        assert_eq!(res, b);
+    }
+
+    #[test]
+    fn test_solve_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_gauss_jordan(b);
+
+        assert!(matches!(res, Err(MatrixError::FailedGaussJordan)));
+    }
+
+    #[test]
+    fn test_solve_invalid_size() {
+        let m = Matrix::new(2, 2, Fraction::from(1)).unwrap();
+
+        let b = vec![Fraction::from(1)];
+
+        let res = m.solve_matrix_with_gauss_jordan(b);
+
+        assert!(matches!(res, Err(MatrixError::InvalidDataSize)));
+    }
+
+    #[test]
+    fn test_solve_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_gauss_jordan(b);
+
+        assert!(matches!(res, Err(MatrixError::NotSquared)));
+    }
 }