As previously noted, the Romans considered the law of succession to be part of the law of things, since succession was construed as a mode of acquisition of rights over things in a mass (per universitatem).

Since, however, it was not merely the assets of the deceased that passed to the heirs but also his debts or obligations, the law of succession is more appropriately treated as an independent section of private law.

The Law of the Twelve Tables already recognized a distinction between intes­tate and testamentary succession.

The rules of intestate succession determined who would be heir, when a person died without a valid will. The law of testamentary succession, on the other hand, consisted of the rules whereby a testator could by way of a will himself determine the devolution of his estate after his death.

3.5.1     

More on the topic As previously noted, the Romans considered the law of succession to be part of the law of things, since succession was construed as a mode of acquisition of rights over things in a mass (per universitatem).:

1. The law of succession addresses the legal destiny of a person’s rights and duties after his death.
2. MODES OF ACQUISITION OF CORPOREAL THINGS
3. The law of things (res)
4. The Roman law of things (ius rerum) or, in contemporary terms, ‘property’, covered a muchbroader field than that encompassed by the modern law of property.
5. The second branch of the threefold division of all of private law which Gaius employs in his Institutes is that of the law of 'things'.
6. Intestate Succession in Justinian's Law
7. Intestate Succession Under the Law of the Twelve Tables
8. The Law of Succession
9. The law of succession
10. LAW OF SUCCESSION