/**
* Adds a participation to the data collector.
*
* @param string $testIdentifier It will look like "Qp0gahJ3RAO3DJ18b0XoUQ"
* @param int $variationIndex
* @throws InvalidArgumentException
*/
public function addParticipation($testIdentifier, $variationIndex)
{
Assert::string($testIdentifier, 'Test identifier must be a string');
Assert::integer($variationIndex, 'Variation index must be integer');
Assert::greaterThan($variationIndex, -1, 'Variation index must be integer >= 0');
$this->participations[$testIdentifier] = $variationIndex;
}