MathPHP\Functions\ArithmeticTest::testSum PHP Метод

    public function testSum()
    {
        // f(x) = x⁴ + 8x³ -13x² -92x + 96
        $f = function ($x) {
            return $x ** 4 + 8 * $x ** 3 - 13 * $x ** 2 - 92 * $x + 96;
        };
        // g(x) = x³ - 12x² + 72x + 27
        $g = function ($x) {
            return $x ** 3 - 12 * $x ** 2 + 72 * $x + 27;
        };
        // Σ(x) = f(x) + g(x) = x⁴ + 9x³ -25x² -20x + 123
        $sum = Arithmetic::add($f, $g);
        // Σ(0) = 123
        $expected = 123;
        $x = $sum(0);
        $this->assertEquals($expected, $x);
        // Σ(5) = 1148
        $expected = 1148;
        $x = $sum(5);
        $this->assertEquals($expected, $x);
        // Σ(-5) = -902
        $expected = -902;
        $x = $sum(-5);
        $this->assertEquals($expected, $x);
        // Σ(100) = 108748123
        $expected = 108748123;
        $x = $sum(100);
        $this->assertEquals($expected, $x);
        // Σ(-100) = 90752123
        $expected = 90752123;
        $x = $sum(-100);
        $this->assertEquals($expected, $x);
    }