A test that renders once because StrictMode is off

A component test passing in the suite and the same component double-fetching in development, because the test environment did not have the double invocation.

// the test
render(<OrderPanel id="8814" />)

// what development does
render(<StrictMode><OrderPanel id="8814" /></StrictMode>)

// wrapping the test the same way makes the test agree
// with development, and fail on the effect that is not
// idempotent.

The test environment and the development environment disagreeing about a diagnostic feature means the diagnostic finds things after the tests have passed, which is backwards. Wrapping the render helper once, globally, cost four failing tests — all four were effects without cleanup, and all four were real.