Do tennis players use doping products?

David Howman expresses his attitude to anti-doping systems in certain sports organizations. While the director general of the WADA seems to be happy with jobs of several sports organizations, he notes that anti-doping systems in other leagues/teams are not suitable.
For example, David Howman praises the International Tennis Federation (ITF) for its anti-doping policy. The director general of the WADA confirms that anti-doping policy is appropriate in tennis.
But when it comes to the National Basketball Association (NBA), it doesn’t want to adopt its anti-doping policy to that of the WADA. It refuses to add some new drug tests in order to catch those who administer steroids and/or other forbidden drugs. That’s why the director general of the WADA states that the anti-doping system of the NBA is not good enough to detect those that dope. He notes that the NBA should add more complicated new methods as well.
David Howman notes that drug tests conducted in tennis have high quality. But there is a defect in tennis’ anti-doping policy. Numerous tests are conducted during competitions. But few tests take place out-of-competition. That’s why ITF’s anti-doping program is also criticized.
Undoubtedly, no one can confirm that anti-doping system of ITF is perfect. It has certain lacks too. But it is quite adequate.
Thus, you should not think that tennis is clean from doping totally. Certain tennis players probably use steroids and/or related preparations. But it is not as tainted, as some other sports.
 Just one tennis player was suspended for administration of banned preparations. However it seems to prove that tennis is not tainted, it is necessary to take in consideration that there are certain ways to prevent positives. As you probably know, the prominent cyclist Lance Armstrong administered steroids and other related medicines and avoided detection much time. Couldn’t tennis players dope and use the same methods?