public function testSubtract()
{
$vector1 = new ColumnVector(1, 2, 3, 4);
$vector2 = new ColumnVector(0.5, 2.5, 2.8, 4.2);
$vector3 = $vector1->subtract($vector2);
$this->assertInstanceOf(ColumnVector::class, $vector3);
$this->assertNotSame($vector3, $vector1);
$this->assertNotSame($vector3, $vector2);
$this->assertEquals([0.5, -0.5, 0.2, -0.2], $vector3->toArray());
}
