function test_playPingPong_numberFifteen()
{
//Arrange
$test_PingPongGenerator = new PingPongGenerator();
$input = "15";
//Act
$result = $test_PingPongGenerator->playPingPong($input);
//Assert
$this->assertEquals("1, 2, ping, 4, pong, ping, 7, 8, ping, pong, 11, ping, 13, 14, ping pong", $result);
}
