public function testCheckPriceAndCurrency()
{
$client = new ChildOfClient();
$res = $client->checkPriceAndCurrency(0.999999, 'BTC');
$this->assertNull($res);
$res = $client->checkPriceAndCurrency(1000, 'USD');
$this->assertNull($res);
$res = $client->checkPriceAndCurrency(0, 'USD');
$this->assertNull($res);
$res = $client->checkPriceAndCurrency(0.01, 'USD');
$this->assertNull($res);
$res = $client->checkPriceAndCurrency(99, 'USD');
$this->assertNull($res);
$res = $client->checkPriceAndCurrency(100.9, 'USD');
$this->assertNull($res);
}