Tests in koalas currently rely on three different helpers on ReusedSQLTestCase for "is this thing equal to…

Tests in koalas currently rely on three different helpers on ReusedSQLTestCase for "is this thing equal to…: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). When I'm writing a new test it's not obvious which one to reach for, and I keep guessing wrong — the choice…