I've never had the chance to participate in a test project but my friends say it's much better than Airdrop. But it's not completely free. There are some projects that do provide testing for their users. But this also means that it takes effort and capital to run these tests. And not all testing projects provide satisfactory results. Sometimes there are testing projects that end up failing and that will cost you money. Unlike Airdrop, if the project fails you will only lose your time and energy.