California Code, Probate Code - PROB § 8250

(a) When a will is contested under Section 8004, the contestant shall file with the court an objection to probate of the will. Thereafter, a summons shall be issued and served, with a copy of the objection, on the persons required by Section 8110 to be served with notice of hearing of a petition for administration of the decedent's estate. The summons shall be issued and served as provided in Chapter 3 (commencing with Section 412.10) and Chapter 4 (commencing with Section 413.10) of Title 5 of Part 2 of the Code of Civil Procedure. The summons shall contain a direction that the persons summoned file with the court a written pleading in response to the contest within 30 days after service of the summons.

(b) A person named as executor in the will is under no duty to defend a contest until the person is appointed personal representative.