php-ml/tests/Math/LinearAlgebra/LUDecompositionTest.php

<?php

declare(strict_types=1);

namespace Phpml\Tests\Math\LinearAlgebra;

use Phpml\Exception\MatrixException;
use Phpml\Math\LinearAlgebra\LUDecomposition;
use Phpml\Math\Matrix;
use PHPUnit\Framework\TestCase;

/**
 * LUDecomposition is used and tested in Matrix::inverse method so not all tests are required
 */
final class LUDecompositionTest extends TestCase
{
    public function testNotSquareMatrix(): void
    {
        $this->expectException(MatrixException::class);

        new LUDecomposition(new Matrix([1, 2, 3, 4, 5]));
    }

    public function testSolveWithInvalidMatrix(): void
    {
        $this->expectException(MatrixException::class);

        $lu = new LUDecomposition(new Matrix([[1, 2], [3, 4]]));
        $lu->solve(new Matrix([1, 2, 3]));
    }

    public function testLowerTriangularFactor(): void
    {
        $lu = new LUDecomposition(new Matrix([[1, 2], [3, 4]]));
        $L = $lu->getL();

        $this->assertInstanceOf(Matrix::class, $L);
        $this->assertSame([[1.0, 0.0], [0.3333333333333333, 1.0]], $L->toArray());
    }

    public function testUpperTriangularFactor(): void
    {
        $lu = new LUDecomposition(new Matrix([[1, 2], [3, 4]]));
        $U = $lu->getU();

        $this->assertInstanceOf(Matrix::class, $U);
        $this->assertSame([[3.0, 4.0], [0.0, 0.6666666666666667]], $U->toArray());
    }
}