I believe the ITF is too lenient in their rules/sanctions regarding refusal to take a test. Their testing control personnel should obviously make it very clear what will happen if one refuses, and there should be witnesses attesting to that. And all players and their support teams should know what sanctions will result without a doubt.
Refusal to take a test is tantamount to refusal to take part in the Anti-Doping programme and should be treated most seriously.
Before a player can play on tour, they are required to sign a consent and agreement form to abide by the rules that includes a section where they agree to participate in the Anti-Doping program. If they don't sign the consent and agreement form, they can't play on tour, simple as that.
A refusal should be considered a violation of the Anti-Doping rules, but moreover of that consent form, and they should be subject to a lifetime ban.
If that rule/sanction were in place, and well known, how many refusals do you think you would you see?
By the way, here is the pertinent rule from the ITF Anti-Doping Programme 2013:
2. Anti-Doping Rule Violations
Doping is defined to be an occurrence of one or more of the Anti Doping Rule Violations and subject to sanction:
...
2.3 Refusing or failing without compelling justification* to submit to Sample collection after notification of Testing as authorised in applicable anti-doping rules, or otherwise evading Sample collection.
* Compelling justification in this rule would mean something where it was unavoidable that they couldn't take the test, like incurring a heart attack or something similar, where the person would be in a life threatening situation if they were forced to take the test. Illness (e.g. dizziness or nausea) or phobias are not compelling justification. Compelling is taken very strictly and narrowly to avoid consequences where testing would be completely undermined.
Respectfully,
masterclass