public function testDiagonal() { $matrix = new Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]); $diagonal = $matrix->diagonal(); static::assertEquals(1, $diagonal->get(0, 0)); static::assertEquals(0, $diagonal->get(0, 1)); static::assertEquals(0, $diagonal->get(0, 2)); static::assertEquals(0, $diagonal->get(1, 0)); static::assertEquals(5, $diagonal->get(1, 1)); static::assertEquals(0, $diagonal->get(1, 2)); static::assertEquals(0, $diagonal->get(2, 0)); static::assertEquals(0, $diagonal->get(2, 1)); static::assertEquals(9, $diagonal->get(2, 2)); }