When writing code and tests, optimize for clarity and idiomatic TypeScript:

1) Prefer async/await when the async function includes a side effect.

// Clear: side effect is explicit
queryFn: async () => {
  await sleep(10)
  fetched = true
  return 'fetched'
}

// Less explicit when side effects are involved
queryFn: () => sleep(10).then(() => {
  fetched = true
  return 'fetched'
})

2) Let TypeScript infer callback types; avoid explicit parameter annotations/imports when they’re redundant.

// Prefer inference
onMutate: async (newTodo, context) => {
  // ...
}
// If the types infer correctly, remove extra imports/annotations.

3) Simplify type-level assertions by removing unnecessary generics/wrappers; use direct indexed access or the minimal expression that captures the intended type.

// Prefer minimal type plumbing
expectTypeOf(queryKey[dataTagSymbol]).toEqualTypeOf<InfiniteData<string>>()