Bevy 0.19 — deterministic testing

When to use this skill

• Systems/plugins need a minimal App harness and direct world assertions.
• Fixed schedules, timers, messages, or observers need deterministic stepping.
• Async work must complete in tests without arbitrary sleeps.
• Rendered output needs capture-based visual regression.

Build the smallest App that owns the behaviour under test, control its clock and inputs, step it explicitly, then inspect world state or emitted output. Do not call App::run() in an ordinary unit/integration test.

Canonical pattern

use bevy::{prelude::*, time::{TimePlugin, TimeUpdateStrategy}};