Add small pivot matrix tests to test_pivot_matrix.py.

tests.json

-{"0.elements": {"test_get_all_atoms.py": ["test_get_all_atoms"], "test_grams_to_mols.py": ["test_grams_to_mols"], "test_molar_mass.py": ["test_molar_mass"]}, "1.balancing": {"test_balance.py": ["test_check_balance_equation"], "test_make_atom_vector.py": ["test_make_atom_vector"], "test_make_compound_matrix.py": ["test_make_compound_matrix"], "test_make_dictionary_solution.py": ["test_make_dictionary_solution"], "test_make_dummy_equation.py": ["test_make_dummy_equation"], "test_make_system_of_equations.py": ["test_make_system_of_equations"], "test_scale_solution.py": ["test_scale_solution"]}, "2.matrix_operations": {"test_negate_matrix.py": ["test_negate_matrix"], "test_transpose_matrix.py": ["test_transpose_matrix"]}, "3.gaussian_elimination": {"test_back_substitute.py": ["test_back_substitute"], "test_gaussian_elimination.py": ["test_gaussian_elimination"], "test_pivot_matrix.py": ["test_pivot_matrix"], "test_ref.py": ["test_ref_zero_row", "test_ref_large_matrix"], "test_scale_matrix.py": ["test_scale_matrix"]}, "4.limiting_reactant": {"test_limiting_reactant.py": ["test_limiting_reactant"], "test_ratio.py": ["test_ratio"]}, "5.theoretical_yield": {"test_theoretical_yield.py": ["test_theoretical_yield"]}}
+{"0.elements": {"test_get_all_atoms.py": ["test_get_all_atoms"], "test_grams_to_mols.py": ["test_grams_to_mols"], "test_molar_mass.py": ["test_molar_mass"]}, "1.balancing": {"test_balance.py": ["test_check_balance_equation"], "test_make_atom_vector.py": ["test_make_atom_vector"], "test_make_compound_matrix.py": ["test_make_compound_matrix"], "test_make_dictionary_solution.py": ["test_make_dictionary_solution"], "test_make_dummy_equation.py": ["test_make_dummy_equation"], "test_make_system_of_equations.py": ["test_make_system_of_equations"], "test_scale_solution.py": ["test_scale_solution"]}, "2.matrix_operations": {"test_negate_matrix.py": ["test_negate_matrix"], "test_transpose_matrix.py": ["test_transpose_matrix"]}, "3.gaussian_elimination": {"test_back_substitute.py": ["test_back_substitute"], "test_gaussian_elimination.py": ["test_gaussian_elimination"], "test_pivot_matrix.py": ["test_pivot_matrix_small", "test_pivot_matrix_large"], "test_ref.py": ["test_ref_zero_row", "test_ref_large_matrix"], "test_scale_matrix.py": ["test_scale_matrix"]}, "4.limiting_reactant": {"test_limiting_reactant.py": ["test_limiting_reactant"], "test_ratio.py": ["test_ratio"]}, "5.theoretical_yield": {"test_theoretical_yield.py": ["test_theoretical_yield"]}}

tests/3.gaussian_elimination/test_pivot_matrix.py

-import random
 import pytest
+from fractions import Fraction
 from support.matrix import MutableRationalMatrix2D
 from tests.helpers.naming import apply_names
 from tests.helpers.matrix_helpers import generate_random_pivot_matrices
@@ -10,8 +10,46 @@ ref_pivot_matrix = driver_import_reference('matrix_operations.pivot_matrix')
 from src.matrix_operations import pivot_matrix
 
 
+_SMALL_PIVOTS = [
+    [[1, 2, 3, 4],
+     [9, 8, 7, 6],
+     [7, 3, 4, 8],
+     ],
+    [[1, 2, 3, 4, 5],
+     [3, 2, 8, 6, 1],
+     [5, 7, 3, 2, 1],
+     [8, 2, 6, 4, 3],
+     ],
+    [[1, 2, 3, 4, 5, 6],
+     [8, 2, 8, 3, 6, 2],
+     [9, 4, 3, 7, 6, 3],
+     [0, 0, 0, 0, 0, 0],
+     [1, 2, 3, 4, 5, 6],
+     ]
+]
+
+
+def _generate_small_pivot_matrices():
+    matrices = []
+    for arr in _SMALL_PIVOTS:
+        mat = MutableRationalMatrix2D((len(arr), len(arr[0])))
+        for i in range(mat.dimensions[0]):
+            for j in range(mat.dimensions[1]):
+                mat[i][j] = Fraction(arr[i][j])
+        matrices.append([mat])
+    return matrices
+
+
+@pytest.mark.parametrize('matrix', apply_names('pivot_matrix', [False], _generate_small_pivot_matrices()))
+def test_pivot_matrix_small(matrix: MutableRationalMatrix2D):
+    for col in range(2, len(matrix)):
+        correct = ref_pivot_matrix(matrix.mutable(), col)
+        out = pivot_matrix(matrix, col)
+        assert correct == out
+
+
 @pytest.mark.parametrize('matrix', apply_names('pivot_matrix', [False], generate_random_pivot_matrices()))
-def test_pivot_matrix(matrix: MutableRationalMatrix2D): 
+def test_pivot_matrix_large(matrix: MutableRationalMatrix2D):
     for col in range(2, len(matrix)):
         correct = ref_pivot_matrix(matrix.mutable(), col)
         out = pivot_matrix(matrix, col)