Generally, you are required to cooperate with your insurance company. Certainly you must do home interviews and fill out whatever forms they send you. You may be required to "take tests;" however, this generally falls under the "Independent Medical Examination" clause of the policy and not all policies provide that you are required to take tests. On the other hand, the insurance company has money that you are trying to get for your disability. If they are not satisfied that you have provided sufficient evidence to have the claim paid, they simply will not pay the claim.
If you have a question about whether a requested test is appropriate under your policy, you should speak to an experienced disability insurance attorney in your area.