> Imagine I want to test a function that operates on quite large application state but not all app state is necessary for that function If not all app state is

> Imagine I want to test a function that operates on quite large application state but not all app state is necessary for that function If not all app state is necessary for that function, it shouldn't require the whole app state in its arguments. type AppState = { databaseConnection: DatabaseConnection, env : "dev" | "prod", apiToken: string, userId: string, ... } & SomeOtherStuff const dropTables = (app: Pick<AppState, "databaseConnection"> & {env: "dev"} ) => app.databaseConnection.dropTables() Conversely, if a function you don't control says it needs the whole app state, believe it.