MathPHP\NumericalAnalysis\RootFinding\BisectionMethodTest::testSolve PHP Method

    public function testSolve()
    {
        // f(x) = x⁴ + 8x³ -13x² -92x + 96
        // This polynomial has 4 roots: 3,1,-8 and -4
        $func = function ($x) {
            return $x ** 4 + 8 * $x ** 3 - 13 * $x ** 2 - 92 * $x + 96;
        };
        $tol = 1.0E-5;
        // Solve for f(x) = 0 where x is -4
        $a = -7;
        $b = 0;
        $expected = -4;
        $x = BisectionMethod::solve($func, $a, $b, $tol);
        $this->assertEquals($expected, $x, '', $tol);
        // Solve for f(x) = 0 where x is -8
        $a = -10;
        $b = -5;
        $expected = -8;
        $x = BisectionMethod::solve($func, $a, $b, $tol);
        $this->assertEquals($expected, $x, '', $tol);
        // Solve for f(x) = 0 where x is 3
        $a = 2;
        $b = 5;
        $expected = 3;
        $x = BisectionMethod::solve($func, $a, $b, $tol);
        $this->assertEquals($expected, $x, '', $tol);
        // Solve for f(x) = 0 where x is 1
        $a = 0;
        $b = 2;
        $expected = 1;
        $x = BisectionMethod::solve($func, $a, $b, $tol);
        $this->assertEquals($expected, $x, '', $tol);
        // Solve for f(x) = 0 where x is 1
        // Switch a and b and test that they get reversed properly
        $b = 0;
        $a = 2;
        $expected = 1;
        $x = BisectionMethod::solve($func, $a, $b, $tol);
        $this->assertEquals($expected, $x, '', $tol);
    }