public function testExceptionNegativeTolerance()
{
$func = function ($x) {
return $x ** 4 + 8 * $x ** 3 - 13 * $x ** 2 - 92 * $x + 96;
};
$tol = -1.0E-5;
$expected = 1;
$p₀ = -1;
$p₁ = 2;
$this->setExpectedException('\\Exception');
$x = SecantMethod::solve($func, $p₀, $p₁, $tol);
}