Islam considers the process of estate planning an essential part of a Muslim's life. A will or "wasiyyah" is a document that outlines a person's wishes regarding the distribution of their assets after their death. Islamic wills must adhere to Islamic law principles or "shariah," which outlines how a person's assets should be divided among their heirs.

Here are some of the basics of Islamic wills and testamentary trusts:

1. Distribution of assets: Islamic law outlines that a person's assets should be distributed among their heirs in a specific manner. The distribution of assets should be done based on the laws of inheritance, which outline the shares each heir is entitled to receive.

2. Appointment of an executor: An executor is responsible for carrying out the deceased's wishes as outlined in their will. In Islamic wills, the executor is the "wasi" appointed by the person creating the will.

3. Charitable giving: Islamic law encourages the practice of charitable giving, and many Muslims include charitable donations in their wills.

4. Creating a testamentary trust: A testamentary trust is a trust that is created through a person's will. In Islamic wills, testamentary trusts can be used to manage assets for the benefit of minor children or disabled heirs.

5. Witnesses: Islamic law requires that a person's will is witnessed by two adult Muslims who are not beneficiaries of the will.

In conclusion, Islamic wills and testamentary trusts are essential to a Muslim's estate planning. It is important to follow the principles of Islamic law when creating a will to ensure that your wishes are carried out in accordance with your beliefs. Consulting with a legal expert with knowledge of Islamic law is recommended.