A gift may be made by a will to a trustee of a trust executed by any trustor or testator (including a funded or unfunded life insurance trust, although the trustor has reserved any or all rights of ownership of the insurance contracts) if (1) the trust is identified in the testator's will and (2) its terms are evidenced either (a) in a written instrument other than a will, executed by the trustor prior to or concurrently with the execution of the testator's will or (b) in the will of a person who has predeceased the testator, regardless of when executed. The existence, size, or character of the corpus of the trust is immaterial to the validity of the gift. Such gift shall not be invalid because the trust is amendable or revocable, or both, or because the trust was amended after the execution of the testator's will or after the testator's death. Unless the will provides otherwise, the property so given shall not be deemed to be held under a testamentary trust of the testator but shall become a part of the trust to which it is given to be administered and disposed of in accordance with the terms of the instrument establishing the trust, including any amendments, made prior to the death of the testator, and regardless of whether made before or after the execution of the will. Unless the will provides otherwise, an express revocation of the trust prior to the testator's death invalidates the gift. Any termination of the trust other than by express revocation does not invalidate the gift. For purposes of this section, the term "gift" includes the exercise of any testamentary power of appointment.