Hired to work for the summer with 〜ことになっている

Grammar Explanation: Past decision still in effect with 〜ことになっている

Rinko (Yamato) interviews for a summer job at her favorite cake shop. Following the interview, she is hired and is set to start work the next day. She’s excited at the various new techniques she’ll learn that she’ll use to make various sweets for her boyfriend, Takeo.

凛子(りんこ):: 「それがいちばん楽(たの)しみかも」; "I think that's what I'm most looking forward to."
たけお:: 「大和(やまと)うれしそうだな」; "Yamato looks happy."; 「ずっと好(す)きだったケーキ屋(や)で働(はたら)けることになってよかった」; "I'm glad it's arranged that she'll be able to work at her most favorite cake shop."