JBZoo\PHPUnit\CalcTest::testChecks PHP Method

    public function testChecks()
    {
        $val = val('-1 usd');
        is(true, $val->isNegative());
        is(false, $val->isPositive());
        is(false, $val->isEmpty());
        $val->set(1);
        is(false, $val->isNegative());
        is(true, $val->isPositive());
        is(false, $val->isEmpty());
        $val->setEmpty();
        is(false, $val->isNegative());
        is(false, $val->isPositive());
        is(true, $val->isEmpty());
    }