def testing_a_noninvertible_matrix_for_invertibility():
# Given
A = Matrix(-4, 2, -2, -3,
9, 6, 2, 6,
0, -5, 1, -5,
0, 0, 0, 0)
# Then
assert A.determinant() == 0
assert not A.is_invertible()
def testing_an_invertible_matrix_for_invertibility():
# Given
A = Matrix(6, 4, 4, 4,
5, 5, 7, 6,
4, -9, 3, -7,
9, 1, 7, -6)
# Then
assert A.determinant() == -2120
assert A.is_invertible()
def test_calculating_the_determinant_of_a_3x3_matrix():
# Given
A = Matrix(1, 2, 6,
-5, 8, -4,
2, 6, 4)
# Then
assert A.cofactor(0, 0) == 56
assert A.cofactor(0, 1) == 12
assert A.cofactor(0, 2) == -46
assert A.determinant() == -196
def test_calculating_the_determinant_of_a_4x4_matrix():
# Given
A = Matrix(-2, -8, 3, 5,
-3, 1, 7, 3,
1, 2, -9, 6,
-6, 7, 7, -9)
# Then
assert A.cofactor(0, 0) == 690
assert A.cofactor(0, 1) == 447
assert A.cofactor(0, 2) == 210
assert A.cofactor(0, 3) == 51
assert A.determinant() == -4071
def test_calculating_the_inverse_of_a_matrix():
# Given
A = Matrix(-5, 2, 6, -8,
1, -5, 1, 8,
7, 7, -6, -7,
1, -3, 7, 4)
B = A.inverse()
# Then
assert A.determinant() == 532
assert A.cofactor(2, 3) == -160
assert equal(B.at(3, 2), -160/532)
assert A.cofactor(3, 2) == 105
assert equal(B.at(2, 3), 105/532)
assert B == Matrix(0.21805, 0.45113, 0.24060, -0.04511,
-0.80827, -1.45677, -0.44361, 0.52068,
-0.07895, -0.22368, -0.05263, 0.19737,
-0.52256, -0.81391, -0.30075, 0.30639)
def test_calculating_the_determinant_of_a_2x2_matrix():
# Given
A = Matrix(1, 5,
-3, 2)
# Then
assert A.determinant() == 17
